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	$141.51	5.320%	$149.0383	$149.04	$149.05	$149.00
Purchase #2	$167.67	8.441%	$181.823	$181.82	$181.80	$181.80
Purchase #3	$109.97	6.861%	$117.515	$117.52	$117.50	$117.50
Purchase #4	$150.43	5.179%	$158.2208	$158.22	$158.20	$158.20
Purchase #5	$153.27	7.742%	$165.1362	$165.14	$165.15	$165.10
Purchase #6	$81.50	9.808%	$89.4935	$89.49	$89.50	$89.50
Purchase #7	$71.57	12.303%	$80.3753	$80.38	$80.40	$80.40
7 purchase totals =	$875.92		$941.6021	$941.61	$941.60	$941.50