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	$233.96	9.321%	$255.7674	$255.77	$255.75	$255.80
Purchase #2	$92.56	13.761%	$105.2972	$105.30	$105.30	$105.30
Purchase #3	$148.84	4.520%	$155.5676	$155.57	$155.55	$155.60
Purchase #4	$106.53	8.851%	$115.959	$115.96	$115.95	$116.00
Purchase #5	$237.41	13.362%	$269.1327	$269.13	$269.15	$269.10
Purchase #6	$55.54	11.708%	$62.0426	$62.04	$62.05	$62.00
Purchase #7	$141.28	4.841%	$148.1194	$148.12	$148.10	$148.10
7 purchase totals =	$1,016.12		$1,111.8859	$1,111.89	$1,111.85	$1,111.90