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	$157.78	5.311%	$166.1597	$166.16	$166.15	$166.20
Purchase #2	$164.93	12.453%	$185.4687	$185.47	$185.45	$185.50
Purchase #3	$205.73	8.130%	$222.4558	$222.46	$222.45	$222.50
Purchase #4	$134.72	12.616%	$151.7163	$151.72	$151.70	$151.70
Purchase #5	$157.41	7.629%	$169.4188	$169.42	$169.40	$169.40
Purchase #6	$179.84	9.461%	$196.8547	$196.85	$196.85	$196.90
Purchase #7	$60.49	12.336%	$67.952	$67.95	$67.95	$68.00
7 purchase totals =	$1,060.90		$1,160.0260	$1,160.03	$1,159.95	$1,160.20