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	$173.78	5.747%	$183.7671	$183.77	$183.75	$183.80
Purchase #2	$95.99	5.162%	$100.945	$100.95	$100.95	$100.90
Purchase #3	$109.95	7.812%	$118.5393	$118.54	$118.55	$118.50
Purchase #4	$98.60	13.282%	$111.6961	$111.70	$111.70	$111.70
Purchase #5	$196.37	4.839%	$205.8723	$205.87	$205.85	$205.90
Purchase #6	$53.67	12.231%	$60.2344	$60.23	$60.25	$60.20
Purchase #7	$98.48	13.134%	$111.4144	$111.41	$111.40	$111.40
7 purchase totals =	$826.84		$892.4686	$892.47	$892.45	$892.40