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	$95.78	4.570%	$100.1571	$100.16	$100.15	$100.20
Purchase #2	$229.69	3.609%	$237.9795	$237.98	$238.00	$238.00
Purchase #3	$154.96	4.351%	$161.7023	$161.70	$161.70	$161.70
Purchase #4	$250.63	6.274%	$266.3545	$266.35	$266.35	$266.40
Purchase #5	$35.86	12.504%	$40.3439	$40.34	$40.35	$40.30
Purchase #6	$35.76	4.219%	$37.2687	$37.27	$37.25	$37.30
Purchase #7	$158.71	6.797%	$169.4975	$169.50	$169.50	$169.50
7 purchase totals =	$961.39		$1,013.3035	$1,013.30	$1,013.30	$1,013.40