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	$85.75	5.548%	$90.5074	$90.51	$90.50	$90.50
Purchase #2	$158.48	8.679%	$172.2345	$172.23	$172.25	$172.20
Purchase #3	$242.78	11.107%	$269.7456	$269.75	$269.75	$269.70
Purchase #4	$196.55	7.406%	$211.1065	$211.11	$211.10	$211.10
Purchase #5	$236.34	11.242%	$262.9093	$262.91	$262.90	$262.90
Purchase #6	$149.80	8.558%	$162.6199	$162.62	$162.60	$162.60
Purchase #7	$169.86	9.465%	$185.9372	$185.94	$185.95	$185.90
7 purchase totals =	$1,239.56		$1,355.0604	$1,355.07	$1,355.05	$1,354.90