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	$105.38	13.250%	$119.3429	$119.34	$119.35	$119.30
Purchase #2	$177.88	7.825%	$191.7991	$191.80	$191.80	$191.80
Purchase #3	$137.29	9.535%	$150.3806	$150.38	$150.40	$150.40
Purchase #4	$246.88	13.591%	$280.4335	$280.43	$280.45	$280.40
Purchase #5	$223.67	11.602%	$249.6202	$249.62	$249.60	$249.60
Purchase #6	$49.26	6.532%	$52.4777	$52.48	$52.50	$52.50
Purchase #7	$95.58	3.772%	$99.1853	$99.19	$99.20	$99.20
7 purchase totals =	$1,035.94		$1,143.2393	$1,143.24	$1,143.30	$1,143.20