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	$142.71	5.820%	$151.0157	$151.02	$151.00	$151.00
Purchase #2	$149.84	4.406%	$156.442	$156.44	$156.45	$156.40
Purchase #3	$180.79	5.737%	$191.1619	$191.16	$191.15	$191.20
Purchase #4	$93.59	13.508%	$106.2321	$106.23	$106.25	$106.20
Purchase #5	$106.46	9.276%	$116.3352	$116.34	$116.35	$116.30
Purchase #6	$250.34	12.849%	$282.5062	$282.51	$282.50	$282.50
Purchase #7	$33.26	12.182%	$37.3117	$37.31	$37.30	$37.30
7 purchase totals =	$956.99		$1,041.0048	$1,041.01	$1,041.00	$1,040.90