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	$105.80	5.677%	$111.8063	$111.81	$111.80	$111.80
Purchase #2	$209.43	13.407%	$237.5083	$237.51	$237.50	$237.50
Purchase #3	$138.65	6.776%	$148.0449	$148.04	$148.05	$148.00
Purchase #4	$102.31	13.468%	$116.0891	$116.09	$116.10	$116.10
Purchase #5	$165.90	7.365%	$178.1185	$178.12	$178.10	$178.10
Purchase #6	$102.64	6.801%	$109.6205	$109.62	$109.60	$109.60
Purchase #7	$187.92	11.274%	$209.1061	$209.11	$209.10	$209.10
7 purchase totals =	$1,012.65		$1,110.2937	$1,110.30	$1,110.25	$1,110.20