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	$83.64	8.147%	$90.4542	$90.45	$90.45	$90.50
Purchase #2	$82.57	9.845%	$90.699	$90.70	$90.70	$90.70
Purchase #3	$162.83	4.830%	$170.6947	$170.69	$170.70	$170.70
Purchase #4	$143.83	9.344%	$157.2695	$157.27	$157.25	$157.30
Purchase #5	$211.62	12.234%	$237.5096	$237.51	$237.50	$237.50
Purchase #6	$44.57	6.803%	$47.6021	$47.60	$47.60	$47.60
Purchase #7	$213.62	13.859%	$243.2256	$243.23	$243.25	$243.20
7 purchase totals =	$942.68		$1,037.4547	$1,037.45	$1,037.45	$1,037.50