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	$97.69	8.647%	$106.1373	$106.14	$106.15	$106.10
Purchase #2	$28.76	13.238%	$32.5672	$32.57	$32.55	$32.60
Purchase #3	$111.73	7.810%	$120.4561	$120.46	$120.45	$120.50
Purchase #4	$77.84	7.359%	$83.5682	$83.57	$83.55	$83.60
Purchase #5	$12.92	3.659%	$13.3927	$13.39	$13.40	$13.40
Purchase #6	$100.27	11.105%	$111.405	$111.41	$111.40	$111.40
Purchase #7	$28.70	8.165%	$31.0434	$31.04	$31.05	$31.00
7 purchase totals =	$457.91		$498.5699	$498.58	$498.55	$498.60