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	$221.28	10.148%	$243.7355	$243.74	$243.75	$243.70
Purchase #2	$166.57	5.667%	$176.0095	$176.01	$176.00	$176.00
Purchase #3	$50.40	12.804%	$56.8532	$56.85	$56.85	$56.90
Purchase #4	$227.79	5.652%	$240.6647	$240.66	$240.65	$240.70
Purchase #5	$59.55	3.267%	$61.4955	$61.50	$61.50	$61.50
Purchase #6	$82.60	8.378%	$89.5202	$89.52	$89.50	$89.50
Purchase #7	$197.51	7.666%	$212.6511	$212.65	$212.65	$212.70
7 purchase totals =	$1,005.70		$1,080.9297	$1,080.93	$1,080.90	$1,081.00