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	$193.81	5.518%	$204.5044	$204.50	$204.50	$204.50
Purchase #2	$61.68	9.660%	$67.6383	$67.64	$67.65	$67.60
Purchase #3	$20.89	7.116%	$22.3765	$22.38	$22.40	$22.40
Purchase #4	$35.78	5.650%	$37.8016	$37.80	$37.80	$37.80
Purchase #5	$237.76	7.736%	$256.1531	$256.15	$256.15	$256.20
Purchase #6	$136.81	9.184%	$149.3746	$149.37	$149.35	$149.40
Purchase #7	$248.64	13.245%	$281.5724	$281.57	$281.55	$281.60
7 purchase totals =	$935.37		$1,019.4209	$1,019.41	$1,019.40	$1,019.50