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	$81.86	9.604%	$89.7218	$89.72	$89.70	$89.70
Purchase #2	$159.97	9.848%	$175.7238	$175.72	$175.70	$175.70
Purchase #3	$214.27	13.614%	$243.4407	$243.44	$243.45	$243.40
Purchase #4	$195.30	8.178%	$211.2716	$211.27	$211.25	$211.30
Purchase #5	$10.30	13.403%	$11.6805	$11.68	$11.70	$11.70
Purchase #6	$197.51	12.859%	$222.9078	$222.91	$222.90	$222.90
Purchase #7	$66.35	8.366%	$71.9008	$71.90	$71.90	$71.90
7 purchase totals =	$925.56		$1,026.6470	$1,026.64	$1,026.60	$1,026.60