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	$243.64	9.374%	$266.4788	$266.48	$266.50	$266.50
Purchase #2	$13.94	9.175%	$15.219	$15.22	$15.20	$15.20
Purchase #3	$31.52	13.215%	$35.6854	$35.69	$35.70	$35.70
Purchase #4	$92.87	6.739%	$99.1285	$99.13	$99.15	$99.10
Purchase #5	$57.50	3.808%	$59.6896	$59.69	$59.70	$59.70
Purchase #6	$99.90	10.685%	$110.5743	$110.57	$110.55	$110.60
Purchase #7	$188.66	9.690%	$206.9412	$206.94	$206.95	$206.90
7 purchase totals =	$728.03		$793.7168	$793.72	$793.75	$793.70