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	$246.54	7.257%	$264.4314	$264.43	$264.45	$264.40
Purchase #2	$29.78	9.102%	$32.4906	$32.49	$32.50	$32.50
Purchase #3	$41.56	8.618%	$45.1416	$45.14	$45.15	$45.10
Purchase #4	$136.86	13.391%	$155.1869	$155.19	$155.20	$155.20
Purchase #5	$93.64	7.262%	$100.4401	$100.44	$100.45	$100.40
Purchase #6	$237.33	11.561%	$264.7677	$264.77	$264.75	$264.80
Purchase #7	$211.69	5.796%	$223.9596	$223.96	$223.95	$224.00
7 purchase totals =	$997.40		$1,086.4179	$1,086.42	$1,086.45	$1,086.40