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	$168.75	12.689%	$190.1627	$190.16	$190.15	$190.20
Purchase #2	$74.59	4.872%	$78.224	$78.22	$78.20	$78.20
Purchase #3	$117.71	12.356%	$132.2542	$132.25	$132.25	$132.30
Purchase #4	$105.36	11.417%	$117.389	$117.39	$117.40	$117.40
Purchase #5	$101.57	7.203%	$108.8861	$108.89	$108.90	$108.90
Purchase #6	$142.92	13.105%	$161.6497	$161.65	$161.65	$161.60
Purchase #7	$221.62	5.258%	$233.2728	$233.27	$233.25	$233.30
7 purchase totals =	$932.52		$1,021.8385	$1,021.83	$1,021.80	$1,021.90