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	$88.69	13.139%	$100.343	$100.34	$100.35	$100.30
Purchase #2	$33.57	5.534%	$35.4278	$35.43	$35.45	$35.40
Purchase #3	$18.29	6.228%	$19.4291	$19.43	$19.45	$19.40
Purchase #4	$154.47	9.555%	$169.2296	$169.23	$169.25	$169.20
Purchase #5	$121.46	8.402%	$131.6651	$131.67	$131.65	$131.70
Purchase #6	$72.42	11.723%	$80.9098	$80.91	$80.90	$80.90
Purchase #7	$189.28	5.529%	$199.7453	$199.75	$199.75	$199.70
7 purchase totals =	$678.18		$736.7497	$736.76	$736.80	$736.60