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	$215.96	4.317%	$225.283	$225.28	$225.30	$225.30
Purchase #2	$213.75	11.874%	$239.1307	$239.13	$239.15	$239.10
Purchase #3	$29.66	12.338%	$33.3195	$33.32	$33.30	$33.30
Purchase #4	$33.28	13.644%	$37.8207	$37.82	$37.80	$37.80
Purchase #5	$231.26	5.114%	$243.0866	$243.09	$243.10	$243.10
Purchase #6	$180.46	10.438%	$199.2964	$199.30	$199.30	$199.30
Purchase #7	$95.89	4.314%	$100.0267	$100.03	$100.05	$100.00
7 purchase totals =	$1,000.26		$1,077.9636	$1,077.97	$1,078.00	$1,077.90