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	$243.41	8.224%	$263.428	$263.43	$263.45	$263.40
Purchase #2	$127.95	9.376%	$139.9466	$139.95	$139.95	$139.90
Purchase #3	$93.39	7.397%	$100.2981	$100.30	$100.30	$100.30
Purchase #4	$182.91	6.788%	$195.3259	$195.33	$195.35	$195.30
Purchase #5	$112.92	5.754%	$119.4174	$119.42	$119.40	$119.40
Purchase #6	$181.34	6.395%	$192.9367	$192.94	$192.95	$192.90
Purchase #7	$76.32	9.853%	$83.8398	$83.84	$83.85	$83.80
7 purchase totals =	$1,018.24		$1,095.1925	$1,095.21	$1,095.25	$1,095.00