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	$224.58	13.274%	$254.3907	$254.39	$254.40	$254.40
Purchase #2	$129.48	11.791%	$144.747	$144.75	$144.75	$144.70
Purchase #3	$55.62	12.488%	$62.5658	$62.57	$62.55	$62.60
Purchase #4	$151.51	13.326%	$171.7002	$171.70	$171.70	$171.70
Purchase #5	$161.38	6.828%	$172.399	$172.40	$172.40	$172.40
Purchase #6	$233.78	13.763%	$265.9551	$265.96	$265.95	$266.00
Purchase #7	$33.84	11.823%	$37.8409	$37.84	$37.85	$37.80
7 purchase totals =	$990.19		$1,109.5987	$1,109.61	$1,109.60	$1,109.60