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	$124.72	13.735%	$141.8503	$141.85	$141.85	$141.90
Purchase #2	$140.67	11.190%	$156.411	$156.41	$156.40	$156.40
Purchase #3	$139.61	9.279%	$152.5644	$152.56	$152.55	$152.60
Purchase #4	$41.70	3.608%	$43.2045	$43.20	$43.20	$43.20
Purchase #5	$216.41	13.670%	$245.9932	$245.99	$246.00	$246.00
Purchase #6	$201.33	8.557%	$218.5578	$218.56	$218.55	$218.60
Purchase #7	$83.50	8.193%	$90.3412	$90.34	$90.35	$90.30
7 purchase totals =	$947.94		$1,048.9224	$1,048.91	$1,048.90	$1,049.00