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	$53.54	10.805%	$59.325	$59.33	$59.35	$59.30
Purchase #2	$119.80	9.184%	$130.8024	$130.80	$130.80	$130.80
Purchase #3	$248.32	9.557%	$272.0519	$272.05	$272.05	$272.10
Purchase #4	$228.34	3.446%	$236.2086	$236.21	$236.20	$236.20
Purchase #5	$138.36	9.776%	$151.8861	$151.89	$151.90	$151.90
Purchase #6	$37.92	13.333%	$42.9759	$42.98	$43.00	$43.00
Purchase #7	$143.98	11.364%	$160.3419	$160.34	$160.35	$160.30
7 purchase totals =	$970.26		$1,053.5918	$1,053.60	$1,053.65	$1,053.60