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	$79.31	3.576%	$82.1461	$82.15	$82.15	$82.10
Purchase #2	$10.73	11.472%	$11.9609	$11.96	$11.95	$12.00
Purchase #3	$86.48	3.305%	$89.3382	$89.34	$89.35	$89.30
Purchase #4	$8.46	6.662%	$9.0236	$9.02	$9.00	$9.00
Purchase #5	$64.39	11.829%	$72.0067	$72.01	$72.00	$72.00
Purchase #6	$203.48	6.559%	$216.8263	$216.83	$216.85	$216.80
Purchase #7	$50.54	5.733%	$53.4375	$53.44	$53.45	$53.40
7 purchase totals =	$503.39		$534.7393	$534.75	$534.75	$534.60