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	$54.55	5.854%	$57.7434	$57.74	$57.75	$57.70
Purchase #2	$61.95	9.519%	$67.847	$67.85	$67.85	$67.80
Purchase #3	$49.57	7.165%	$53.1217	$53.12	$53.10	$53.10
Purchase #4	$236.69	12.581%	$266.468	$266.47	$266.45	$266.50
Purchase #5	$58.39	4.487%	$61.01	$61.01	$61.00	$61.00
Purchase #6	$57.79	3.220%	$59.6508	$59.65	$59.65	$59.70
Purchase #7	$37.91	4.767%	$39.7172	$39.72	$39.70	$39.70
7 purchase totals =	$556.85		$605.5581	$605.56	$605.50	$605.50