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	$161.51	7.538%	$173.6846	$173.68	$173.70	$173.70
Purchase #2	$121.29	4.840%	$127.1604	$127.16	$127.15	$127.20
Purchase #3	$166.31	13.357%	$188.524	$188.52	$188.50	$188.50
Purchase #4	$78.33	3.473%	$81.0504	$81.05	$81.05	$81.10
Purchase #5	$45.46	13.645%	$51.663	$51.66	$51.65	$51.70
Purchase #6	$197.54	10.647%	$218.5721	$218.57	$218.55	$218.60
Purchase #7	$93.83	6.385%	$99.821	$99.82	$99.80	$99.80
7 purchase totals =	$864.27		$940.4755	$940.46	$940.40	$940.60