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	$114.30	4.631%	$119.5932	$119.59	$119.60	$119.60
Purchase #2	$117.54	8.752%	$127.8271	$127.83	$127.85	$127.80
Purchase #3	$209.27	4.178%	$218.0133	$218.01	$218.00	$218.00
Purchase #4	$66.39	13.176%	$75.1375	$75.14	$75.15	$75.10
Purchase #5	$231.71	13.301%	$262.5297	$262.53	$262.55	$262.50
Purchase #6	$28.37	9.259%	$30.9968	$31.00	$31.00	$31.00
Purchase #7	$180.92	4.123%	$188.3793	$188.38	$188.40	$188.40
7 purchase totals =	$948.50		$1,022.4769	$1,022.48	$1,022.55	$1,022.40