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	$133.31	13.293%	$151.0309	$151.03	$151.05	$151.00
Purchase #2	$222.47	11.441%	$247.9228	$247.92	$247.90	$247.90
Purchase #3	$32.64	10.513%	$36.0714	$36.07	$36.05	$36.10
Purchase #4	$96.66	3.739%	$100.2741	$100.27	$100.25	$100.30
Purchase #5	$127.73	6.694%	$136.2802	$136.28	$136.30	$136.30
Purchase #6	$179.31	13.697%	$203.8701	$203.87	$203.85	$203.90
Purchase #7	$220.92	3.387%	$228.4026	$228.40	$228.40	$228.40
7 purchase totals =	$1,013.04		$1,103.8521	$1,103.84	$1,103.80	$1,103.90