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	$62.42	10.791%	$69.1557	$69.16	$69.15	$69.20
Purchase #2	$56.26	6.269%	$59.7869	$59.79	$59.80	$59.80
Purchase #3	$33.85	11.158%	$37.627	$37.63	$37.65	$37.60
Purchase #4	$139.99	10.462%	$154.6358	$154.64	$154.65	$154.60
Purchase #5	$154.83	12.261%	$173.8137	$173.81	$173.80	$173.80
Purchase #6	$174.49	12.619%	$196.5089	$196.51	$196.50	$196.50
Purchase #7	$8.36	6.424%	$8.897	$8.90	$8.90	$8.90
7 purchase totals =	$630.20		$700.4250	$700.44	$700.45	$700.40