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	$48.38	12.317%	$54.339	$54.34	$54.35	$54.30
Purchase #2	$175.51	4.233%	$182.9393	$182.94	$182.95	$182.90
Purchase #3	$124.30	13.575%	$141.1737	$141.17	$141.15	$141.20
Purchase #4	$41.60	5.319%	$43.8127	$43.81	$43.80	$43.80
Purchase #5	$96.31	10.212%	$106.1452	$106.15	$106.15	$106.10
Purchase #6	$206.55	11.698%	$230.7122	$230.71	$230.70	$230.70
Purchase #7	$245.72	3.549%	$254.4406	$254.44	$254.45	$254.40
7 purchase totals =	$938.37		$1,013.5627	$1,013.56	$1,013.55	$1,013.40