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	$102.31	8.330%	$110.8324	$110.83	$110.85	$110.80
Purchase #2	$22.42	12.578%	$25.24	$25.24	$25.25	$25.20
Purchase #3	$141.44	9.368%	$154.6901	$154.69	$154.70	$154.70
Purchase #4	$115.98	6.624%	$123.6625	$123.66	$123.65	$123.70
Purchase #5	$77.97	4.814%	$81.7235	$81.72	$81.70	$81.70
Purchase #6	$55.81	8.561%	$60.5879	$60.59	$60.60	$60.60
Purchase #7	$100.50	9.312%	$109.8586	$109.86	$109.85	$109.90
7 purchase totals =	$616.43		$666.5950	$666.59	$666.60	$666.60