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	$91.53	5.381%	$96.4552	$96.46	$96.45	$96.50
Purchase #2	$204.29	13.179%	$231.2134	$231.21	$231.20	$231.20
Purchase #3	$147.83	9.577%	$161.9877	$161.99	$162.00	$162.00
Purchase #4	$88.27	13.782%	$100.4354	$100.44	$100.45	$100.40
Purchase #5	$176.79	6.383%	$188.0745	$188.07	$188.05	$188.10
Purchase #6	$141.86	11.481%	$158.1469	$158.15	$158.15	$158.10
Purchase #7	$33.82	11.526%	$37.7181	$37.72	$37.70	$37.70
7 purchase totals =	$884.39		$974.0312	$974.04	$974.00	$974.00