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	$198.82	8.480%	$215.6799	$215.68	$215.70	$215.70
Purchase #2	$161.28	11.123%	$179.2192	$179.22	$179.20	$179.20
Purchase #3	$90.42	5.356%	$95.2629	$95.26	$95.25	$95.30
Purchase #4	$206.30	6.260%	$219.2144	$219.21	$219.20	$219.20
Purchase #5	$126.38	8.526%	$137.1552	$137.16	$137.15	$137.20
Purchase #6	$56.83	4.513%	$59.3947	$59.39	$59.40	$59.40
Purchase #7	$70.28	11.586%	$78.4226	$78.42	$78.40	$78.40
7 purchase totals =	$910.31		$984.3489	$984.34	$984.30	$984.40