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	$223.94	12.582%	$252.1161	$252.12	$252.10	$252.10
Purchase #2	$237.80	11.550%	$265.2659	$265.27	$265.25	$265.30
Purchase #3	$104.36	6.579%	$111.2258	$111.23	$111.25	$111.20
Purchase #4	$41.82	6.572%	$44.5684	$44.57	$44.55	$44.60
Purchase #5	$40.73	4.485%	$42.5567	$42.56	$42.55	$42.60
Purchase #6	$241.81	8.119%	$261.4426	$261.44	$261.45	$261.40
Purchase #7	$239.88	3.111%	$247.3427	$247.34	$247.35	$247.30
7 purchase totals =	$1,130.34		$1,224.5182	$1,224.53	$1,224.50	$1,224.50