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	$210.73	8.413%	$228.4587	$228.46	$228.45	$228.50
Purchase #2	$159.85	11.789%	$178.6947	$178.69	$178.70	$178.70
Purchase #3	$42.54	13.597%	$48.3242	$48.32	$48.30	$48.30
Purchase #4	$10.38	3.147%	$10.7067	$10.71	$10.70	$10.70
Purchase #5	$205.54	11.632%	$229.4484	$229.45	$229.45	$229.40
Purchase #6	$176.39	11.503%	$196.6801	$196.68	$196.70	$196.70
Purchase #7	$200.95	11.146%	$223.3479	$223.35	$223.35	$223.30
7 purchase totals =	$1,006.38		$1,115.6607	$1,115.66	$1,115.65	$1,115.60