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	$235.72	6.836%	$251.8338	$251.83	$251.85	$251.80
Purchase #2	$140.83	7.160%	$150.9134	$150.91	$150.90	$150.90
Purchase #3	$62.31	6.220%	$66.1857	$66.19	$66.20	$66.20
Purchase #4	$127.56	3.150%	$131.5781	$131.58	$131.60	$131.60
Purchase #5	$201.27	6.221%	$213.791	$213.79	$213.80	$213.80
Purchase #6	$30.80	7.679%	$33.1651	$33.17	$33.15	$33.20
Purchase #7	$157.52	4.471%	$164.5627	$164.56	$164.55	$164.60
7 purchase totals =	$956.01		$1,012.0298	$1,012.03	$1,012.05	$1,012.10