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	$245.70	3.197%	$253.555	$253.56	$253.55	$253.60
Purchase #2	$243.33	13.378%	$275.8827	$275.88	$275.90	$275.90
Purchase #3	$168.34	10.278%	$185.642	$185.64	$185.65	$185.60
Purchase #4	$163.32	5.618%	$172.4953	$172.50	$172.50	$172.50
Purchase #5	$47.40	4.115%	$49.3505	$49.35	$49.35	$49.40
Purchase #6	$60.77	10.438%	$67.1132	$67.11	$67.10	$67.10
Purchase #7	$242.95	7.127%	$260.265	$260.27	$260.25	$260.30
7 purchase totals =	$1,171.81		$1,264.3037	$1,264.31	$1,264.30	$1,264.40