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	$74.79	10.280%	$82.4784	$82.48	$82.50	$82.50
Purchase #2	$249.77	9.121%	$272.5515	$272.55	$272.55	$272.60
Purchase #3	$137.86	9.852%	$151.442	$151.44	$151.45	$151.40
Purchase #4	$16.89	13.366%	$19.1475	$19.15	$19.15	$19.10
Purchase #5	$95.35	4.758%	$99.8868	$99.89	$99.90	$99.90
Purchase #6	$180.27	5.410%	$190.0226	$190.02	$190.00	$190.00
Purchase #7	$199.35	9.706%	$218.6989	$218.70	$218.70	$218.70
7 purchase totals =	$954.28		$1,034.2277	$1,034.23	$1,034.25	$1,034.20