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	$79.68	11.618%	$88.9372	$88.94	$88.95	$88.90
Purchase #2	$34.59	4.397%	$36.1109	$36.11	$36.10	$36.10
Purchase #3	$144.38	3.213%	$149.0189	$149.02	$149.00	$149.00
Purchase #4	$98.50	13.554%	$111.8507	$111.85	$111.85	$111.90
Purchase #5	$31.86	7.510%	$34.2527	$34.25	$34.25	$34.30
Purchase #6	$221.27	3.854%	$229.7977	$229.80	$229.80	$229.80
Purchase #7	$199.31	11.601%	$222.432	$222.43	$222.45	$222.40
7 purchase totals =	$809.59		$872.4001	$872.40	$872.40	$872.40