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	$22.54	4.310%	$23.5115	$23.51	$23.50	$23.50
Purchase #2	$181.97	9.231%	$198.7677	$198.77	$198.75	$198.80
Purchase #3	$231.60	10.289%	$255.4293	$255.43	$255.45	$255.40
Purchase #4	$179.59	11.236%	$199.7687	$199.77	$199.75	$199.80
Purchase #5	$91.55	5.530%	$96.6127	$96.61	$96.60	$96.60
Purchase #6	$189.26	11.770%	$211.5359	$211.54	$211.55	$211.50
Purchase #7	$58.43	11.707%	$65.2704	$65.27	$65.25	$65.30
7 purchase totals =	$954.94		$1,050.8962	$1,050.90	$1,050.85	$1,050.90