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	$82.92	12.788%	$93.5238	$93.52	$93.50	$93.50
Purchase #2	$77.86	4.752%	$81.5599	$81.56	$81.55	$81.60
Purchase #3	$218.98	13.382%	$248.2839	$248.28	$248.30	$248.30
Purchase #4	$51.26	11.281%	$57.0426	$57.04	$57.05	$57.00
Purchase #5	$38.48	10.660%	$42.582	$42.58	$42.60	$42.60
Purchase #6	$113.47	11.264%	$126.2513	$126.25	$126.25	$126.30
Purchase #7	$53.33	12.282%	$59.88	$59.88	$59.90	$59.90
7 purchase totals =	$636.30		$709.1235	$709.11	$709.15	$709.20