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	$143.37	4.638%	$150.0195	$150.02	$150.00	$150.00
Purchase #2	$119.65	4.522%	$125.0606	$125.06	$125.05	$125.10
Purchase #3	$106.93	4.594%	$111.8424	$111.84	$111.85	$111.80
Purchase #4	$195.95	10.353%	$216.2367	$216.24	$216.25	$216.20
Purchase #5	$140.34	7.158%	$150.3855	$150.39	$150.40	$150.40
Purchase #6	$90.55	12.434%	$101.809	$101.81	$101.80	$101.80
Purchase #7	$89.52	12.326%	$100.5542	$100.55	$100.55	$100.60
7 purchase totals =	$886.31		$955.9079	$955.91	$955.90	$955.90