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	$71.74	12.250%	$80.5282	$80.53	$80.55	$80.50
Purchase #2	$99.90	3.778%	$103.6742	$103.67	$103.65	$103.70
Purchase #3	$33.73	13.777%	$38.377	$38.38	$38.40	$38.40
Purchase #4	$199.94	5.829%	$211.5945	$211.59	$211.60	$211.60
Purchase #5	$51.77	6.726%	$55.2521	$55.25	$55.25	$55.30
Purchase #6	$119.90	5.266%	$126.2139	$126.21	$126.20	$126.20
Purchase #7	$98.44	12.741%	$110.9822	$110.98	$111.00	$111.00
7 purchase totals =	$675.42		$726.6221	$726.61	$726.65	$726.70