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	$99.85	3.317%	$103.162	$103.16	$103.15	$103.20
Purchase #2	$47.45	10.588%	$52.474	$52.47	$52.45	$52.50
Purchase #3	$24.88	12.437%	$27.9743	$27.97	$27.95	$28.00
Purchase #4	$179.48	10.314%	$197.9916	$197.99	$198.00	$198.00
Purchase #5	$64.99	4.348%	$67.8158	$67.82	$67.80	$67.80
Purchase #6	$159.33	8.358%	$172.6468	$172.65	$172.65	$172.60
Purchase #7	$59.47	7.335%	$63.8321	$63.83	$63.85	$63.80
7 purchase totals =	$635.45		$685.8966	$685.89	$685.85	$685.90