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	$135.68	10.503%	$149.9305	$149.93	$149.95	$149.90
Purchase #2	$64.47	10.543%	$71.2671	$71.27	$71.25	$71.30
Purchase #3	$152.93	12.532%	$172.0952	$172.10	$172.10	$172.10
Purchase #4	$42.42	5.747%	$44.8579	$44.86	$44.85	$44.90
Purchase #5	$175.64	11.689%	$196.1706	$196.17	$196.15	$196.20
Purchase #6	$138.34	6.263%	$147.0042	$147.00	$147.00	$147.00
Purchase #7	$53.66	10.675%	$59.3882	$59.39	$59.40	$59.40
7 purchase totals =	$763.14		$840.7137	$840.72	$840.70	$840.80