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	$55.90	10.461%	$61.7477	$61.75	$61.75	$61.70
Purchase #2	$31.28	5.863%	$33.1139	$33.11	$33.10	$33.10
Purchase #3	$53.51	11.289%	$59.5507	$59.55	$59.55	$59.60
Purchase #4	$203.76	13.597%	$231.4652	$231.47	$231.45	$231.50
Purchase #5	$10.87	11.309%	$12.0993	$12.10	$12.10	$12.10
Purchase #6	$91.37	7.747%	$98.4484	$98.45	$98.45	$98.40
Purchase #7	$60.68	6.828%	$64.8232	$64.82	$64.80	$64.80
7 purchase totals =	$507.37		$561.2484	$561.25	$561.20	$561.20