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	$248.80	4.829%	$260.8146	$260.81	$260.80	$260.80
Purchase #2	$220.96	7.151%	$236.7608	$236.76	$236.75	$236.80
Purchase #3	$89.39	12.721%	$100.7613	$100.76	$100.75	$100.80
Purchase #4	$243.76	13.301%	$276.1825	$276.18	$276.20	$276.20
Purchase #5	$95.57	10.824%	$105.9145	$105.91	$105.90	$105.90
Purchase #6	$66.60	9.254%	$72.7632	$72.76	$72.75	$72.80
Purchase #7	$10.95	7.254%	$11.7443	$11.74	$11.75	$11.70
7 purchase totals =	$976.03		$1,064.9412	$1,064.92	$1,064.90	$1,065.00