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	$250.50	4.267%	$261.1888	$261.19	$261.20	$261.20
Purchase #2	$155.88	4.306%	$162.5922	$162.59	$162.60	$162.60
Purchase #3	$83.32	4.173%	$86.7969	$86.80	$86.80	$86.80
Purchase #4	$55.67	7.323%	$59.7467	$59.75	$59.75	$59.70
Purchase #5	$123.91	13.536%	$140.6825	$140.68	$140.70	$140.70
Purchase #6	$113.78	12.679%	$128.2062	$128.21	$128.20	$128.20
Purchase #7	$234.80	5.529%	$247.7821	$247.78	$247.80	$247.80
7 purchase totals =	$1,017.86		$1,086.9954	$1,087.00	$1,087.05	$1,087.00