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	$71.90	3.671%	$74.5394	$74.54	$74.55	$74.50
Purchase #2	$29.48	11.581%	$32.8941	$32.89	$32.90	$32.90
Purchase #3	$46.40	5.594%	$48.9956	$49.00	$49.00	$49.00
Purchase #4	$149.96	9.625%	$164.3937	$164.39	$164.40	$164.40
Purchase #5	$104.69	8.333%	$113.4138	$113.41	$113.40	$113.40
Purchase #6	$69.50	10.649%	$76.9011	$76.90	$76.90	$76.90
Purchase #7	$128.50	11.217%	$142.9138	$142.91	$142.90	$142.90
7 purchase totals =	$600.43		$654.0515	$654.04	$654.05	$654.00