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	$202.38	12.495%	$227.6674	$227.67	$227.65	$227.70
Purchase #2	$33.62	10.527%	$37.1592	$37.16	$37.15	$37.20
Purchase #3	$185.43	5.465%	$195.5637	$195.56	$195.55	$195.60
Purchase #4	$136.35	10.162%	$150.2059	$150.21	$150.20	$150.20
Purchase #5	$97.68	11.822%	$109.2277	$109.23	$109.25	$109.20
Purchase #6	$234.62	11.459%	$261.5051	$261.51	$261.50	$261.50
Purchase #7	$160.69	4.253%	$167.5241	$167.52	$167.50	$167.50
7 purchase totals =	$1,050.77		$1,148.8531	$1,148.86	$1,148.80	$1,148.90