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	$131.99	12.847%	$148.9468	$148.95	$148.95	$148.90
Purchase #2	$239.56	4.179%	$249.5712	$249.57	$249.55	$249.60
Purchase #3	$240.55	6.207%	$255.4809	$255.48	$255.50	$255.50
Purchase #4	$36.65	10.130%	$40.3626	$40.36	$40.35	$40.40
Purchase #5	$176.48	10.751%	$195.4534	$195.45	$195.45	$195.50
Purchase #6	$58.54	10.562%	$64.723	$64.72	$64.70	$64.70
Purchase #7	$85.48	3.379%	$88.3684	$88.37	$88.35	$88.40
7 purchase totals =	$969.25		$1,042.9063	$1,042.90	$1,042.85	$1,043.00