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	$94.84	11.370%	$105.6233	$105.62	$105.60	$105.60
Purchase #2	$114.79	12.129%	$128.7129	$128.71	$128.70	$128.70
Purchase #3	$48.55	13.308%	$55.011	$55.01	$55.00	$55.00
Purchase #4	$94.79	12.817%	$106.9392	$106.94	$106.95	$106.90
Purchase #5	$127.96	7.275%	$137.2691	$137.27	$137.25	$137.30
Purchase #6	$127.99	7.490%	$137.5765	$137.58	$137.60	$137.60
Purchase #7	$239.58	8.704%	$260.433	$260.43	$260.45	$260.40
7 purchase totals =	$848.50		$931.5650	$931.56	$931.55	$931.50