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	$91.98	11.556%	$102.6092	$102.61	$102.60	$102.60
Purchase #2	$190.81	10.849%	$211.511	$211.51	$211.50	$211.50
Purchase #3	$64.91	11.592%	$72.4344	$72.43	$72.45	$72.40
Purchase #4	$148.80	3.644%	$154.2223	$154.22	$154.20	$154.20
Purchase #5	$204.49	12.408%	$229.8631	$229.86	$229.85	$229.90
Purchase #6	$165.30	11.873%	$184.9261	$184.93	$184.95	$184.90
Purchase #7	$161.74	6.310%	$171.9458	$171.95	$171.95	$171.90
7 purchase totals =	$1,028.03		$1,127.5119	$1,127.51	$1,127.50	$1,127.40