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	$85.41	3.326%	$88.2507	$88.25	$88.25	$88.30
Purchase #2	$9.39	13.387%	$10.647	$10.65	$10.65	$10.60
Purchase #3	$109.65	6.181%	$116.4275	$116.43	$116.45	$116.40
Purchase #4	$52.32	5.358%	$55.1233	$55.12	$55.10	$55.10
Purchase #5	$164.89	12.541%	$185.5689	$185.57	$185.55	$185.60
Purchase #6	$208.65	12.318%	$234.3515	$234.35	$234.35	$234.40
Purchase #7	$174.96	9.399%	$191.4045	$191.40	$191.40	$191.40
7 purchase totals =	$805.27		$881.7734	$881.77	$881.75	$881.80