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	$100.73	4.483%	$105.2457	$105.25	$105.25	$105.20
Purchase #2	$195.90	8.789%	$213.1177	$213.12	$213.10	$213.10
Purchase #3	$161.54	6.612%	$172.221	$172.22	$172.20	$172.20
Purchase #4	$249.98	6.376%	$265.9187	$265.92	$265.90	$265.90
Purchase #5	$66.61	11.434%	$74.2262	$74.23	$74.25	$74.20
Purchase #6	$117.35	5.515%	$123.8219	$123.82	$123.80	$123.80
Purchase #7	$190.96	3.189%	$197.0497	$197.05	$197.05	$197.00
7 purchase totals =	$1,083.07		$1,151.6009	$1,151.61	$1,151.55	$1,151.40