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	$76.62	11.598%	$85.5064	$85.51	$85.50	$85.50
Purchase #2	$59.30	10.486%	$65.5182	$65.52	$65.50	$65.50
Purchase #3	$195.56	8.187%	$211.5705	$211.57	$211.55	$211.60
Purchase #4	$226.64	3.733%	$235.1005	$235.10	$235.10	$235.10
Purchase #5	$144.30	8.362%	$156.3664	$156.37	$156.35	$156.40
Purchase #6	$64.28	10.818%	$71.2338	$71.23	$71.25	$71.20
Purchase #7	$150.78	13.626%	$171.3253	$171.33	$171.35	$171.30
7 purchase totals =	$917.48		$996.6211	$996.63	$996.60	$996.60