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	$179.63	9.507%	$196.7074	$196.71	$196.70	$196.70
Purchase #2	$78.35	10.245%	$86.377	$86.38	$86.40	$86.40
Purchase #3	$11.55	5.257%	$12.1572	$12.16	$12.15	$12.20
Purchase #4	$221.56	13.130%	$250.6508	$250.65	$250.65	$250.70
Purchase #5	$157.58	8.820%	$171.4786	$171.48	$171.50	$171.50
Purchase #6	$170.81	8.347%	$185.0675	$185.07	$185.05	$185.10
Purchase #7	$175.76	12.483%	$197.7001	$197.70	$197.70	$197.70
7 purchase totals =	$995.24		$1,100.1386	$1,100.15	$1,100.15	$1,100.30