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	$91.93	9.329%	$100.5061	$100.51	$100.50	$100.50
Purchase #2	$193.68	6.603%	$206.4687	$206.47	$206.45	$206.50
Purchase #3	$52.54	4.411%	$54.8575	$54.86	$54.85	$54.90
Purchase #4	$90.59	8.519%	$98.3074	$98.31	$98.30	$98.30
Purchase #5	$103.72	11.871%	$116.0326	$116.03	$116.05	$116.00
Purchase #6	$68.96	8.337%	$74.7092	$74.71	$74.70	$74.70
Purchase #7	$125.51	12.831%	$141.6142	$141.61	$141.60	$141.60
7 purchase totals =	$726.93		$792.4957	$792.50	$792.45	$792.50