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	$202.28	12.472%	$227.5084	$227.51	$227.50	$227.50
Purchase #2	$154.80	3.698%	$160.5245	$160.52	$160.50	$160.50
Purchase #3	$146.86	6.138%	$155.8743	$155.87	$155.85	$155.90
Purchase #4	$16.99	3.123%	$17.5206	$17.52	$17.50	$17.50
Purchase #5	$114.88	13.716%	$130.6369	$130.64	$130.65	$130.60
Purchase #6	$242.85	12.535%	$273.2912	$273.29	$273.30	$273.30
Purchase #7	$119.52	7.840%	$128.8904	$128.89	$128.90	$128.90
7 purchase totals =	$998.18		$1,094.2463	$1,094.24	$1,094.20	$1,094.20