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	$184.72	8.172%	$199.8153	$199.82	$199.80	$199.80
Purchase #2	$65.67	10.450%	$72.5325	$72.53	$72.55	$72.50
Purchase #3	$228.32	11.340%	$254.2115	$254.21	$254.20	$254.20
Purchase #4	$162.81	4.530%	$170.1853	$170.19	$170.20	$170.20
Purchase #5	$214.88	9.522%	$235.3409	$235.34	$235.35	$235.30
Purchase #6	$27.58	7.360%	$29.6099	$29.61	$29.60	$29.60
Purchase #7	$64.60	10.394%	$71.3145	$71.31	$71.30	$71.30
7 purchase totals =	$948.58		$1,033.0099	$1,033.01	$1,033.00	$1,032.90