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	$200.48	7.772%	$216.0613	$216.06	$216.05	$216.10
Purchase #2	$108.31	12.536%	$121.8877	$121.89	$121.90	$121.90
Purchase #3	$148.70	8.142%	$160.8072	$160.81	$160.80	$160.80
Purchase #4	$240.38	6.454%	$255.8941	$255.89	$255.90	$255.90
Purchase #5	$136.84	6.480%	$145.7072	$145.71	$145.70	$145.70
Purchase #6	$68.43	4.770%	$71.6941	$71.69	$71.70	$71.70
Purchase #7	$104.66	7.279%	$112.2782	$112.28	$112.30	$112.30
7 purchase totals =	$1,007.80		$1,084.3298	$1,084.33	$1,084.35	$1,084.40