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	$227.95	11.249%	$253.5921	$253.59	$253.60	$253.60
Purchase #2	$91.90	13.339%	$104.1585	$104.16	$104.15	$104.20
Purchase #3	$96.58	9.570%	$105.8227	$105.82	$105.80	$105.80
Purchase #4	$29.96	9.453%	$32.7921	$32.79	$32.80	$32.80
Purchase #5	$29.44	11.851%	$32.9289	$32.93	$32.95	$32.90
Purchase #6	$31.33	7.140%	$33.567	$33.57	$33.55	$33.60
Purchase #7	$33.93	12.480%	$38.1645	$38.16	$38.15	$38.20
7 purchase totals =	$541.09		$601.0258	$601.02	$601.00	$601.10