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	$99.65	5.459%	$105.0899	$105.09	$105.10	$105.10
Purchase #2	$187.88	9.130%	$205.0334	$205.03	$205.05	$205.00
Purchase #3	$102.98	3.848%	$106.9427	$106.94	$106.95	$106.90
Purchase #4	$86.73	3.227%	$89.5288	$89.53	$89.55	$89.50
Purchase #5	$247.96	12.699%	$279.4484	$279.45	$279.45	$279.40
Purchase #6	$191.67	8.577%	$208.1095	$208.11	$208.10	$208.10
Purchase #7	$32.42	7.361%	$34.8064	$34.81	$34.80	$34.80
7 purchase totals =	$949.29		$1,028.9591	$1,028.96	$1,029.00	$1,028.80