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	$146.56	4.637%	$153.356	$153.36	$153.35	$153.40
Purchase #2	$31.51	5.209%	$33.1514	$33.15	$33.15	$33.20
Purchase #3	$42.71	12.673%	$48.1226	$48.12	$48.10	$48.10
Purchase #4	$156.59	13.564%	$177.8299	$177.83	$177.85	$177.80
Purchase #5	$244.30	8.275%	$264.5158	$264.52	$264.50	$264.50
Purchase #6	$77.92	9.197%	$85.0863	$85.09	$85.10	$85.10
Purchase #7	$126.90	10.135%	$139.7613	$139.76	$139.75	$139.80
7 purchase totals =	$826.49		$901.8233	$901.83	$901.80	$901.90