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	$221.68	5.397%	$233.6441	$233.64	$233.65	$233.60
Purchase #2	$42.76	6.562%	$45.5659	$45.57	$45.55	$45.60
Purchase #3	$159.53	8.700%	$173.4091	$173.41	$173.40	$173.40
Purchase #4	$97.97	10.526%	$108.2823	$108.28	$108.30	$108.30
Purchase #5	$132.81	3.559%	$137.5367	$137.54	$137.55	$137.50
Purchase #6	$219.80	12.532%	$247.3453	$247.35	$247.35	$247.30
Purchase #7	$209.81	6.332%	$223.0952	$223.10	$223.10	$223.10
7 purchase totals =	$1,084.36		$1,168.8786	$1,168.89	$1,168.90	$1,168.80