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	$31.52	12.751%	$35.5391	$35.54	$35.55	$35.50
Purchase #2	$59.38	12.781%	$66.9694	$66.97	$66.95	$67.00
Purchase #3	$189.52	13.283%	$214.6939	$214.69	$214.70	$214.70
Purchase #4	$145.76	11.468%	$162.4758	$162.48	$162.50	$162.50
Purchase #5	$15.61	12.361%	$17.5396	$17.54	$17.55	$17.50
Purchase #6	$39.53	8.536%	$42.9043	$42.90	$42.90	$42.90
Purchase #7	$208.51	6.131%	$221.2937	$221.29	$221.30	$221.30
7 purchase totals =	$689.83		$761.4158	$761.41	$761.45	$761.40