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	$131.34	11.241%	$146.1039	$146.10	$146.10	$146.10
Purchase #2	$153.85	12.205%	$172.6274	$172.63	$172.65	$172.60
Purchase #3	$98.66	4.516%	$103.1155	$103.12	$103.10	$103.10
Purchase #4	$218.93	9.218%	$239.111	$239.11	$239.10	$239.10
Purchase #5	$220.47	11.256%	$245.2861	$245.29	$245.30	$245.30
Purchase #6	$68.96	12.333%	$77.4648	$77.46	$77.45	$77.50
Purchase #7	$42.62	6.801%	$45.5186	$45.52	$45.50	$45.50
7 purchase totals =	$934.83		$1,029.2273	$1,029.23	$1,029.20	$1,029.20