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	$220.68	10.416%	$243.666	$243.67	$243.65	$243.70
Purchase #2	$227.33	6.242%	$241.5199	$241.52	$241.50	$241.50
Purchase #3	$6.42	8.197%	$6.9462	$6.95	$6.95	$6.90
Purchase #4	$125.32	4.854%	$131.403	$131.40	$131.40	$131.40
Purchase #5	$83.93	6.485%	$89.3729	$89.37	$89.35	$89.40
Purchase #6	$123.84	11.279%	$137.8079	$137.81	$137.80	$137.80
Purchase #7	$156.41	5.598%	$165.1658	$165.17	$165.15	$165.20
7 purchase totals =	$943.93		$1,015.8817	$1,015.89	$1,015.80	$1,015.90