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	$249.67	8.796%	$271.631	$271.63	$271.65	$271.60
Purchase #2	$10.51	4.449%	$10.9776	$10.98	$11.00	$11.00
Purchase #3	$168.33	6.640%	$179.5071	$179.51	$179.50	$179.50
Purchase #4	$97.39	4.162%	$101.4434	$101.44	$101.45	$101.40
Purchase #5	$246.67	10.470%	$272.4963	$272.50	$272.50	$272.50
Purchase #6	$162.53	10.542%	$179.6639	$179.66	$179.65	$179.70
Purchase #7	$42.63	6.496%	$45.3992	$45.40	$45.40	$45.40
7 purchase totals =	$977.73		$1,061.1185	$1,061.12	$1,061.15	$1,061.10