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	$97.83	13.726%	$111.2581	$111.26	$111.25	$111.30
Purchase #2	$113.73	6.625%	$121.2646	$121.26	$121.25	$121.30
Purchase #3	$202.70	10.565%	$224.1153	$224.12	$224.10	$224.10
Purchase #4	$152.32	12.850%	$171.8931	$171.89	$171.90	$171.90
Purchase #5	$47.67	4.651%	$49.8871	$49.89	$49.90	$49.90
Purchase #6	$41.62	12.631%	$46.877	$46.88	$46.90	$46.90
Purchase #7	$70.46	12.852%	$79.5155	$79.52	$79.50	$79.50
7 purchase totals =	$726.33		$804.8107	$804.82	$804.80	$804.90