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	$61.50	6.444%	$65.4631	$65.46	$65.45	$65.50
Purchase #2	$185.27	11.483%	$206.5446	$206.54	$206.55	$206.50
Purchase #3	$184.93	7.238%	$198.3152	$198.32	$198.30	$198.30
Purchase #4	$74.71	13.398%	$84.7196	$84.72	$84.70	$84.70
Purchase #5	$80.65	11.457%	$89.8901	$89.89	$89.90	$89.90
Purchase #6	$10.72	12.632%	$12.0742	$12.07	$12.05	$12.10
Purchase #7	$159.96	7.754%	$172.3633	$172.36	$172.35	$172.40
7 purchase totals =	$757.74		$829.3701	$829.36	$829.30	$829.40