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	$223.52	4.134%	$232.7603	$232.76	$232.75	$232.80
Purchase #2	$235.72	8.440%	$255.6148	$255.61	$255.60	$255.60
Purchase #3	$110.90	7.676%	$119.4127	$119.41	$119.40	$119.40
Purchase #4	$244.31	4.132%	$254.4049	$254.40	$254.40	$254.40
Purchase #5	$88.63	4.415%	$92.543	$92.54	$92.55	$92.50
Purchase #6	$110.77	4.465%	$115.7159	$115.72	$115.70	$115.70
Purchase #7	$32.65	8.843%	$35.5372	$35.54	$35.55	$35.50
7 purchase totals =	$1,046.50		$1,105.9888	$1,105.98	$1,105.95	$1,105.90