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	$73.47	12.373%	$82.5604	$82.56	$82.55	$82.60
Purchase #2	$79.60	4.709%	$83.3484	$83.35	$83.35	$83.30
Purchase #3	$229.95	9.667%	$252.1793	$252.18	$252.20	$252.20
Purchase #4	$222.56	4.872%	$233.4031	$233.40	$233.40	$233.40
Purchase #5	$209.81	6.529%	$223.5085	$223.51	$223.50	$223.50
Purchase #6	$198.88	3.788%	$206.4136	$206.41	$206.40	$206.40
Purchase #7	$124.89	4.119%	$130.0342	$130.03	$130.05	$130.00
7 purchase totals =	$1,139.16		$1,211.4475	$1,211.44	$1,211.45	$1,211.40