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	$98.63	13.488%	$111.9332	$111.93	$111.95	$111.90
Purchase #2	$121.76	5.355%	$128.2802	$128.28	$128.30	$128.30
Purchase #3	$249.62	6.330%	$265.4209	$265.42	$265.40	$265.40
Purchase #4	$54.98	10.490%	$60.7474	$60.75	$60.75	$60.70
Purchase #5	$225.78	9.635%	$247.5339	$247.53	$247.55	$247.50
Purchase #6	$164.39	12.671%	$185.2199	$185.22	$185.20	$185.20
Purchase #7	$25.59	3.131%	$26.3912	$26.39	$26.40	$26.40
7 purchase totals =	$940.75		$1,025.5267	$1,025.52	$1,025.55	$1,025.40