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	$26.72	3.785%	$27.7314	$27.73	$27.75	$27.70
Purchase #2	$90.61	5.463%	$95.56	$95.56	$95.55	$95.60
Purchase #3	$246.40	11.492%	$274.7163	$274.72	$274.70	$274.70
Purchase #4	$195.73	6.571%	$208.5914	$208.59	$208.60	$208.60
Purchase #5	$42.66	12.350%	$47.9285	$47.93	$47.95	$47.90
Purchase #6	$216.62	11.735%	$242.0404	$242.04	$242.05	$242.00
Purchase #7	$90.88	9.670%	$99.6681	$99.67	$99.65	$99.70
7 purchase totals =	$909.62		$996.2361	$996.24	$996.25	$996.20