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	$52.53	12.698%	$59.2003	$59.20	$59.20	$59.20
Purchase #2	$217.54	13.523%	$246.9579	$246.96	$246.95	$247.00
Purchase #3	$184.50	13.136%	$208.7359	$208.74	$208.75	$208.70
Purchase #4	$197.77	5.841%	$209.3217	$209.32	$209.30	$209.30
Purchase #5	$196.48	10.109%	$216.3422	$216.34	$216.35	$216.30
Purchase #6	$78.74	5.261%	$82.8825	$82.88	$82.90	$82.90
Purchase #7	$148.27	13.400%	$168.1382	$168.14	$168.15	$168.10
7 purchase totals =	$1,075.83		$1,191.5787	$1,191.58	$1,191.60	$1,191.50