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	$238.93	8.505%	$259.251	$259.25	$259.25	$259.30
Purchase #2	$12.82	11.145%	$14.2488	$14.25	$14.25	$14.20
Purchase #3	$241.61	9.677%	$264.9906	$264.99	$265.00	$265.00
Purchase #4	$189.43	6.818%	$202.3453	$202.35	$202.35	$202.30
Purchase #5	$80.39	4.315%	$83.8588	$83.86	$83.85	$83.90
Purchase #6	$55.85	10.808%	$61.8863	$61.89	$61.90	$61.90
Purchase #7	$149.56	4.488%	$156.2723	$156.27	$156.25	$156.30
7 purchase totals =	$968.59		$1,042.8531	$1,042.86	$1,042.85	$1,042.90