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	$185.64	7.386%	$199.3514	$199.35	$199.35	$199.40
Purchase #2	$194.38	11.530%	$216.792	$216.79	$216.80	$216.80
Purchase #3	$191.98	4.204%	$200.0508	$200.05	$200.05	$200.10
Purchase #4	$161.71	10.425%	$178.5683	$178.57	$178.55	$178.60
Purchase #5	$131.61	3.468%	$136.1742	$136.17	$136.15	$136.20
Purchase #6	$179.30	11.727%	$200.3265	$200.33	$200.35	$200.30
Purchase #7	$120.84	5.202%	$127.1261	$127.13	$127.15	$127.10
7 purchase totals =	$1,165.46		$1,258.3893	$1,258.39	$1,258.40	$1,258.50