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	$198.96	8.437%	$215.7463	$215.75	$215.75	$215.70
Purchase #2	$88.44	13.592%	$100.4608	$100.46	$100.45	$100.50
Purchase #3	$234.61	10.381%	$258.9649	$258.96	$258.95	$259.00
Purchase #4	$50.62	13.503%	$57.4552	$57.46	$57.45	$57.50
Purchase #5	$197.92	13.116%	$223.8792	$223.88	$223.90	$223.90
Purchase #6	$97.83	6.868%	$104.549	$104.55	$104.55	$104.50
Purchase #7	$90.39	8.641%	$98.2006	$98.20	$98.20	$98.20
7 purchase totals =	$958.77		$1,059.2560	$1,059.26	$1,059.25	$1,059.30