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	$63.72	12.385%	$71.6117	$71.61	$71.60	$71.60
Purchase #2	$152.30	5.335%	$160.4252	$160.43	$160.45	$160.40
Purchase #3	$218.52	10.249%	$240.9161	$240.92	$240.90	$240.90
Purchase #4	$93.39	6.251%	$99.2278	$99.23	$99.25	$99.20
Purchase #5	$71.93	8.439%	$78.0002	$78.00	$78.00	$78.00
Purchase #6	$129.92	5.528%	$137.102	$137.10	$137.10	$137.10
Purchase #7	$244.75	8.788%	$266.2586	$266.26	$266.25	$266.30
7 purchase totals =	$974.53		$1,053.5416	$1,053.55	$1,053.55	$1,053.50