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	$177.25	9.623%	$194.3068	$194.31	$194.30	$194.30
Purchase #2	$216.91	8.316%	$234.9482	$234.95	$234.95	$234.90
Purchase #3	$148.98	5.281%	$156.8476	$156.85	$156.85	$156.80
Purchase #4	$104.25	6.759%	$111.2963	$111.30	$111.30	$111.30
Purchase #5	$207.70	12.452%	$233.5628	$233.56	$233.55	$233.60
Purchase #6	$52.39	6.231%	$55.6544	$55.65	$55.65	$55.70
Purchase #7	$242.42	5.505%	$255.7652	$255.77	$255.75	$255.80
7 purchase totals =	$1,149.90		$1,242.3813	$1,242.39	$1,242.35	$1,242.40