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	$152.32	12.634%	$171.5641	$171.56	$171.55	$171.60
Purchase #2	$179.90	9.336%	$196.6955	$196.70	$196.70	$196.70
Purchase #3	$158.30	11.110%	$175.8871	$175.89	$175.90	$175.90
Purchase #4	$226.45	5.251%	$238.3409	$238.34	$238.35	$238.30
Purchase #5	$230.82	6.113%	$244.93	$244.93	$244.95	$244.90
Purchase #6	$238.40	3.662%	$247.1302	$247.13	$247.15	$247.10
Purchase #7	$148.84	8.385%	$161.3202	$161.32	$161.30	$161.30
7 purchase totals =	$1,335.03		$1,435.8680	$1,435.87	$1,435.90	$1,435.80