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	$232.78	4.782%	$243.9115	$243.91	$243.90	$243.90
Purchase #2	$211.77	11.729%	$236.6085	$236.61	$236.60	$236.60
Purchase #3	$64.93	4.279%	$67.7084	$67.71	$67.70	$67.70
Purchase #4	$40.68	4.431%	$42.4825	$42.48	$42.50	$42.50
Purchase #5	$140.38	6.375%	$149.3292	$149.33	$149.35	$149.30
Purchase #6	$71.98	6.665%	$76.7775	$76.78	$76.80	$76.80
Purchase #7	$219.89	10.605%	$243.2093	$243.21	$243.20	$243.20
7 purchase totals =	$982.41		$1,060.0269	$1,060.03	$1,060.05	$1,060.00