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	$121.28	4.493%	$126.7291	$126.73	$126.75	$126.70
Purchase #2	$105.31	11.507%	$117.428	$117.43	$117.45	$117.40
Purchase #3	$228.96	11.499%	$255.2881	$255.29	$255.30	$255.30
Purchase #4	$91.47	12.773%	$103.1535	$103.15	$103.15	$103.20
Purchase #5	$169.98	10.470%	$187.7769	$187.78	$187.80	$187.80
Purchase #6	$137.57	7.361%	$147.6965	$147.70	$147.70	$147.70
Purchase #7	$176.45	11.213%	$196.2353	$196.24	$196.25	$196.20
7 purchase totals =	$1,031.02		$1,134.3074	$1,134.32	$1,134.40	$1,134.30