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	$141.26	8.254%	$152.9196	$152.92	$152.90	$152.90
Purchase #2	$226.80	7.382%	$243.5424	$243.54	$243.55	$243.50
Purchase #3	$24.43	7.367%	$26.2298	$26.23	$26.25	$26.20
Purchase #4	$65.31	10.607%	$72.2374	$72.24	$72.25	$72.20
Purchase #5	$63.40	13.326%	$71.8487	$71.85	$71.85	$71.80
Purchase #6	$122.25	9.612%	$134.0007	$134.00	$134.00	$134.00
Purchase #7	$48.98	7.830%	$52.8151	$52.82	$52.80	$52.80
7 purchase totals =	$692.43		$753.5937	$753.60	$753.60	$753.40