Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$204.77	9.652%	$224.5344	$224.53	$224.55	$224.50
Purchase #2	$98.79	13.397%	$112.0249	$112.02	$112.00	$112.00
Purchase #3	$149.83	11.579%	$167.1788	$167.18	$167.20	$167.20
Purchase #4	$156.29	7.762%	$168.4212	$168.42	$168.40	$168.40
Purchase #5	$141.74	11.515%	$158.0614	$158.06	$158.05	$158.10
Purchase #6	$191.82	9.422%	$209.8933	$209.89	$209.90	$209.90
Purchase #7	$120.65	11.710%	$134.7781	$134.78	$134.80	$134.80
7 purchase totals =	$1,063.89		$1,174.8921	$1,174.88	$1,174.90	$1,174.90