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	$93.80	5.818%	$99.2573	$99.26	$99.25	$99.30
Purchase #2	$200.94	10.259%	$221.5544	$221.55	$221.55	$221.60
Purchase #3	$124.48	3.262%	$128.5405	$128.54	$128.55	$128.50
Purchase #4	$40.96	10.530%	$45.2731	$45.27	$45.25	$45.30
Purchase #5	$240.69	7.540%	$258.838	$258.84	$258.85	$258.80
Purchase #6	$188.98	5.530%	$199.4306	$199.43	$199.45	$199.40
Purchase #7	$225.95	8.262%	$244.618	$244.62	$244.60	$244.60
7 purchase totals =	$1,115.80		$1,197.5119	$1,197.51	$1,197.50	$1,197.50