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	$242.86	8.585%	$263.7095	$263.71	$263.70	$263.70
Purchase #2	$40.54	13.632%	$46.0664	$46.07	$46.05	$46.10
Purchase #3	$130.39	13.505%	$147.9992	$148.00	$148.00	$148.00
Purchase #4	$229.39	9.354%	$250.8471	$250.85	$250.85	$250.80
Purchase #5	$212.43	12.139%	$238.2169	$238.22	$238.20	$238.20
Purchase #6	$249.81	10.825%	$276.8519	$276.85	$276.85	$276.90
Purchase #7	$106.27	5.252%	$111.8513	$111.85	$111.85	$111.90
7 purchase totals =	$1,211.69		$1,335.5423	$1,335.55	$1,335.50	$1,335.60