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	$65.39	11.240%	$72.7398	$72.74	$72.75	$72.70
Purchase #2	$30.90	3.688%	$32.0396	$32.04	$32.05	$32.00
Purchase #3	$62.29	8.336%	$67.4825	$67.48	$67.50	$67.50
Purchase #4	$55.68	7.399%	$59.7998	$59.80	$59.80	$59.80
Purchase #5	$81.60	13.504%	$92.6193	$92.62	$92.60	$92.60
Purchase #6	$39.33	11.520%	$43.8608	$43.86	$43.85	$43.90
Purchase #7	$167.45	6.562%	$178.4381	$178.44	$178.45	$178.40
7 purchase totals =	$502.64		$546.9799	$546.98	$547.00	$546.90