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	$249.89	4.356%	$260.7752	$260.78	$260.80	$260.80
Purchase #2	$130.47	7.842%	$140.7015	$140.70	$140.70	$140.70
Purchase #3	$90.89	10.816%	$100.7207	$100.72	$100.70	$100.70
Purchase #4	$36.38	3.132%	$37.5194	$37.52	$37.50	$37.50
Purchase #5	$56.25	10.413%	$62.1073	$62.11	$62.10	$62.10
Purchase #6	$94.88	8.701%	$103.1355	$103.14	$103.15	$103.10
Purchase #7	$166.45	12.213%	$186.7785	$186.78	$186.80	$186.80
7 purchase totals =	$825.21		$891.7381	$891.75	$891.75	$891.70