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	$205.35	8.124%	$222.0326	$222.03	$222.05	$222.00
Purchase #2	$230.98	8.605%	$250.8558	$250.86	$250.85	$250.90
Purchase #3	$192.97	13.305%	$218.6447	$218.64	$218.65	$218.60
Purchase #4	$28.76	12.251%	$32.2834	$32.28	$32.30	$32.30
Purchase #5	$20.54	9.343%	$22.4591	$22.46	$22.45	$22.50
Purchase #6	$194.35	7.528%	$208.9807	$208.98	$209.00	$209.00
Purchase #7	$137.90	9.400%	$150.8626	$150.86	$150.85	$150.90
7 purchase totals =	$1,010.85		$1,106.1189	$1,106.11	$1,106.15	$1,106.20