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	$129.82	13.578%	$147.447	$147.45	$147.45	$147.40
Purchase #2	$50.86	7.794%	$54.824	$54.82	$54.80	$54.80
Purchase #3	$105.56	13.855%	$120.1853	$120.19	$120.20	$120.20
Purchase #4	$138.55	8.496%	$150.3212	$150.32	$150.30	$150.30
Purchase #5	$242.59	6.712%	$258.8726	$258.87	$258.85	$258.90
Purchase #6	$70.88	3.621%	$73.4466	$73.45	$73.45	$73.40
Purchase #7	$204.71	11.782%	$228.8289	$228.83	$228.85	$228.80
7 purchase totals =	$942.97		$1,033.9256	$1,033.93	$1,033.90	$1,033.80