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	$211.64	5.295%	$222.8463	$222.85	$222.85	$222.80
Purchase #2	$80.55	4.171%	$83.9097	$83.91	$83.90	$83.90
Purchase #3	$29.99	7.353%	$32.1952	$32.20	$32.20	$32.20
Purchase #4	$35.58	9.743%	$39.0466	$39.05	$39.05	$39.00
Purchase #5	$168.91	13.247%	$191.2855	$191.29	$191.30	$191.30
Purchase #6	$226.75	3.480%	$234.6409	$234.64	$234.65	$234.60
Purchase #7	$53.30	12.165%	$59.7839	$59.78	$59.80	$59.80
7 purchase totals =	$806.72		$863.7081	$863.72	$863.75	$863.60