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	$186.45	12.409%	$209.5866	$209.59	$209.60	$209.60
Purchase #2	$57.50	4.194%	$59.9116	$59.91	$59.90	$59.90
Purchase #3	$62.37	6.173%	$66.2201	$66.22	$66.20	$66.20
Purchase #4	$245.95	3.551%	$254.6837	$254.68	$254.70	$254.70
Purchase #5	$67.41	7.449%	$72.4314	$72.43	$72.45	$72.40
Purchase #6	$74.43	4.272%	$77.6096	$77.61	$77.60	$77.60
Purchase #7	$198.35	4.229%	$206.7382	$206.74	$206.75	$206.70
7 purchase totals =	$892.46		$947.1812	$947.18	$947.20	$947.10