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	$218.32	11.675%	$243.8089	$243.81	$243.80	$243.80
Purchase #2	$173.66	10.167%	$191.316	$191.32	$191.30	$191.30
Purchase #3	$72.52	13.346%	$82.1985	$82.20	$82.20	$82.20
Purchase #4	$22.89	8.402%	$24.8132	$24.81	$24.80	$24.80
Purchase #5	$63.42	3.544%	$65.6676	$65.67	$65.65	$65.70
Purchase #6	$142.69	5.433%	$150.4423	$150.44	$150.45	$150.40
Purchase #7	$14.32	13.518%	$16.2558	$16.26	$16.25	$16.30
7 purchase totals =	$707.82		$774.5023	$774.51	$774.45	$774.50