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	$82.94	12.790%	$93.548	$93.55	$93.55	$93.50
Purchase #2	$115.54	10.301%	$127.4418	$127.44	$127.45	$127.40
Purchase #3	$66.91	7.333%	$71.8165	$71.82	$71.80	$71.80
Purchase #4	$215.52	9.572%	$236.1496	$236.15	$236.15	$236.10
Purchase #5	$117.37	6.108%	$124.539	$124.54	$124.55	$124.50
Purchase #6	$138.48	11.837%	$154.8719	$154.87	$154.85	$154.90
Purchase #7	$236.54	11.367%	$263.4275	$263.43	$263.45	$263.40
7 purchase totals =	$973.30		$1,071.7943	$1,071.80	$1,071.80	$1,071.60