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	$200.69	6.448%	$213.6305	$213.63	$213.65	$213.60
Purchase #2	$73.84	6.476%	$78.6219	$78.62	$78.60	$78.60
Purchase #3	$139.74	11.221%	$155.4202	$155.42	$155.40	$155.40
Purchase #4	$185.36	10.420%	$204.6745	$204.67	$204.65	$204.70
Purchase #5	$189.85	11.858%	$212.3624	$212.36	$212.35	$212.40
Purchase #6	$100.50	4.818%	$105.3421	$105.34	$105.35	$105.30
Purchase #7	$62.94	13.641%	$71.5256	$71.53	$71.55	$71.50
7 purchase totals =	$952.92		$1,041.5772	$1,041.57	$1,041.55	$1,041.50