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	$41.30	13.163%	$46.7363	$46.74	$46.75	$46.70
Purchase #2	$137.58	10.678%	$152.2708	$152.27	$152.25	$152.30
Purchase #3	$89.33	11.304%	$99.4279	$99.43	$99.45	$99.40
Purchase #4	$152.27	11.294%	$169.4674	$169.47	$169.45	$169.50
Purchase #5	$129.66	13.142%	$146.6999	$146.70	$146.70	$146.70
Purchase #6	$238.25	10.504%	$263.2758	$263.28	$263.30	$263.30
Purchase #7	$114.92	4.304%	$119.8662	$119.87	$119.85	$119.90
7 purchase totals =	$903.31		$997.7443	$997.76	$997.75	$997.80