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	$212.71	5.203%	$223.7773	$223.78	$223.80	$223.80
Purchase #2	$244.82	3.323%	$252.9554	$252.96	$252.95	$253.00
Purchase #3	$35.51	13.634%	$40.3514	$40.35	$40.35	$40.40
Purchase #4	$36.86	4.565%	$38.5427	$38.54	$38.55	$38.50
Purchase #5	$223.45	8.543%	$242.5393	$242.54	$242.55	$242.50
Purchase #6	$31.43	13.768%	$35.7573	$35.76	$35.75	$35.80
Purchase #7	$168.90	12.601%	$190.1831	$190.18	$190.20	$190.20
7 purchase totals =	$953.68		$1,024.1065	$1,024.11	$1,024.15	$1,024.20