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	$78.46	11.234%	$87.2742	$87.27	$87.25	$87.30
Purchase #2	$194.51	9.269%	$212.5391	$212.54	$212.55	$212.50
Purchase #3	$113.32	11.503%	$126.3552	$126.36	$126.35	$126.40
Purchase #4	$130.72	5.386%	$137.7606	$137.76	$137.75	$137.80
Purchase #5	$130.66	7.237%	$140.1159	$140.12	$140.10	$140.10
Purchase #6	$178.70	9.730%	$196.0875	$196.09	$196.10	$196.10
Purchase #7	$59.48	5.129%	$62.5307	$62.53	$62.55	$62.50
7 purchase totals =	$885.85		$962.6632	$962.67	$962.65	$962.70