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	$188.43	10.785%	$208.7522	$208.75	$208.75	$208.80
Purchase #2	$210.93	6.363%	$224.3515	$224.35	$224.35	$224.40
Purchase #3	$245.99	9.398%	$269.1081	$269.11	$269.10	$269.10
Purchase #4	$51.51	5.819%	$54.5074	$54.51	$54.50	$54.50
Purchase #5	$24.63	7.144%	$26.3896	$26.39	$26.40	$26.40
Purchase #6	$66.68	7.296%	$71.545	$71.55	$71.55	$71.50
Purchase #7	$117.43	5.224%	$123.5645	$123.56	$123.55	$123.60
7 purchase totals =	$905.60		$978.2183	$978.22	$978.20	$978.30