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	$84.98	12.448%	$95.5583	$95.56	$95.55	$95.60
Purchase #2	$84.66	6.122%	$89.8429	$89.84	$89.85	$89.80
Purchase #3	$120.63	3.746%	$125.1488	$125.15	$125.15	$125.10
Purchase #4	$9.38	13.164%	$10.6148	$10.61	$10.60	$10.60
Purchase #5	$50.63	5.729%	$53.5306	$53.53	$53.55	$53.50
Purchase #6	$233.60	13.244%	$264.538	$264.54	$264.55	$264.50
Purchase #7	$223.90	6.528%	$238.5162	$238.52	$238.50	$238.50
7 purchase totals =	$807.78		$877.7496	$877.75	$877.75	$877.60