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	$90.69	12.497%	$102.0235	$102.02	$102.00	$102.00
Purchase #2	$136.51	11.367%	$152.0271	$152.03	$152.05	$152.00
Purchase #3	$174.88	5.519%	$184.5316	$184.53	$184.55	$184.50
Purchase #4	$40.53	13.425%	$45.9712	$45.97	$45.95	$46.00
Purchase #5	$52.28	5.328%	$55.0655	$55.07	$55.05	$55.10
Purchase #6	$70.64	10.600%	$78.1278	$78.13	$78.15	$78.10
Purchase #7	$119.28	13.579%	$135.477	$135.48	$135.50	$135.50
7 purchase totals =	$684.81		$753.2237	$753.23	$753.25	$753.20