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	$206.59	13.701%	$234.8949	$234.89	$234.90	$234.90
Purchase #2	$172.79	11.282%	$192.2842	$192.28	$192.30	$192.30
Purchase #3	$90.86	5.630%	$95.9754	$95.98	$96.00	$96.00
Purchase #4	$166.34	9.583%	$182.2804	$182.28	$182.30	$182.30
Purchase #5	$115.64	6.624%	$123.3	$123.30	$123.30	$123.30
Purchase #6	$30.93	3.536%	$32.0237	$32.02	$32.00	$32.00
Purchase #7	$37.49	3.773%	$38.9045	$38.90	$38.90	$38.90
7 purchase totals =	$820.64		$899.6631	$899.65	$899.70	$899.70