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	$38.65	7.260%	$41.456	$41.46	$41.45	$41.50
Purchase #2	$210.94	8.247%	$228.3362	$228.34	$228.35	$228.30
Purchase #3	$54.90	7.751%	$59.1553	$59.16	$59.15	$59.20
Purchase #4	$191.49	4.632%	$200.3598	$200.36	$200.35	$200.40
Purchase #5	$155.96	3.256%	$161.0381	$161.04	$161.05	$161.00
Purchase #6	$28.55	13.860%	$32.507	$32.51	$32.50	$32.50
Purchase #7	$158.68	10.728%	$175.7032	$175.70	$175.70	$175.70
7 purchase totals =	$839.17		$898.5556	$898.57	$898.55	$898.60