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	$52.54	12.511%	$59.1133	$59.11	$59.10	$59.10
Purchase #2	$244.46	7.432%	$262.6283	$262.63	$262.65	$262.60
Purchase #3	$46.78	13.742%	$53.2085	$53.21	$53.20	$53.20
Purchase #4	$167.73	6.808%	$179.1491	$179.15	$179.15	$179.10
Purchase #5	$42.56	8.364%	$46.1197	$46.12	$46.10	$46.10
Purchase #6	$19.77	8.134%	$21.3781	$21.38	$21.40	$21.40
Purchase #7	$126.45	8.741%	$137.503	$137.50	$137.50	$137.50
7 purchase totals =	$700.29		$759.1000	$759.10	$759.10	$759.00