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	$176.62	7.328%	$189.5627	$189.56	$189.55	$189.60
Purchase #2	$38.49	9.268%	$42.0573	$42.06	$42.05	$42.10
Purchase #3	$39.45	7.536%	$42.423	$42.42	$42.40	$42.40
Purchase #4	$51.25	3.726%	$53.1596	$53.16	$53.15	$53.20
Purchase #5	$158.54	6.440%	$168.75	$168.75	$168.75	$168.80
Purchase #6	$96.83	3.811%	$100.5202	$100.52	$100.50	$100.50
Purchase #7	$182.82	13.165%	$206.8883	$206.89	$206.90	$206.90
7 purchase totals =	$744.00		$803.3611	$803.36	$803.30	$803.50