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	$246.57	7.636%	$265.3981	$265.40	$265.40	$265.40
Purchase #2	$95.53	4.294%	$99.6321	$99.63	$99.65	$99.60
Purchase #3	$236.35	11.634%	$263.847	$263.85	$263.85	$263.80
Purchase #4	$218.64	3.236%	$225.7152	$225.72	$225.70	$225.70
Purchase #5	$150.42	12.191%	$168.7577	$168.76	$168.75	$168.80
Purchase #6	$82.52	4.870%	$86.5387	$86.54	$86.55	$86.50
Purchase #7	$51.91	5.452%	$54.7401	$54.74	$54.75	$54.70
7 purchase totals =	$1,081.94		$1,164.6289	$1,164.64	$1,164.65	$1,164.50