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	$161.30	4.634%	$168.7746	$168.77	$168.75	$168.80
Purchase #2	$178.86	12.365%	$200.976	$200.98	$201.00	$201.00
Purchase #3	$211.78	6.123%	$224.7473	$224.75	$224.75	$224.70
Purchase #4	$84.59	8.628%	$91.8884	$91.89	$91.90	$91.90
Purchase #5	$86.30	4.775%	$90.4208	$90.42	$90.40	$90.40
Purchase #6	$169.35	9.497%	$185.4332	$185.43	$185.45	$185.40
Purchase #7	$105.96	4.434%	$110.6583	$110.66	$110.65	$110.70
7 purchase totals =	$998.14		$1,072.8986	$1,072.90	$1,072.90	$1,072.90