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	$81.56	13.173%	$92.3039	$92.30	$92.30	$92.30
Purchase #2	$172.50	4.515%	$180.2884	$180.29	$180.30	$180.30
Purchase #3	$43.63	7.845%	$47.0528	$47.05	$47.05	$47.10
Purchase #4	$24.79	10.810%	$27.4698	$27.47	$27.45	$27.50
Purchase #5	$55.70	10.326%	$61.4516	$61.45	$61.45	$61.50
Purchase #6	$217.78	7.368%	$233.826	$233.83	$233.85	$233.80
Purchase #7	$117.70	11.392%	$131.1084	$131.11	$131.10	$131.10
7 purchase totals =	$713.66		$773.5009	$773.50	$773.50	$773.60