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	$151.43	10.319%	$167.0561	$167.06	$167.05	$167.10
Purchase #2	$162.96	9.236%	$178.011	$178.01	$178.00	$178.00
Purchase #3	$156.77	7.757%	$168.9306	$168.93	$168.95	$168.90
Purchase #4	$84.52	7.776%	$91.0923	$91.09	$91.10	$91.10
Purchase #5	$160.72	11.398%	$179.0389	$179.04	$179.05	$179.00
Purchase #6	$143.35	3.192%	$147.9257	$147.93	$147.95	$147.90
Purchase #7	$14.50	7.315%	$15.5607	$15.56	$15.55	$15.60
7 purchase totals =	$874.25		$947.6153	$947.62	$947.65	$947.60