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	$200.64	13.373%	$227.4716	$227.47	$227.45	$227.50
Purchase #2	$248.31	4.807%	$260.2463	$260.25	$260.25	$260.20
Purchase #3	$173.34	6.399%	$184.432	$184.43	$184.45	$184.40
Purchase #4	$57.74	3.653%	$59.8492	$59.85	$59.85	$59.80
Purchase #5	$27.51	5.248%	$28.9537	$28.95	$28.95	$29.00
Purchase #6	$11.85	12.388%	$13.318	$13.32	$13.30	$13.30
Purchase #7	$104.51	4.395%	$109.1032	$109.10	$109.10	$109.10
7 purchase totals =	$823.90		$883.3740	$883.37	$883.35	$883.30