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	$238.58	8.797%	$259.5679	$259.57	$259.55	$259.60
Purchase #2	$19.27	11.335%	$21.4543	$21.45	$21.45	$21.50
Purchase #3	$180.91	8.709%	$196.6655	$196.67	$196.65	$196.70
Purchase #4	$195.47	11.775%	$218.4866	$218.49	$218.50	$218.50
Purchase #5	$65.69	9.752%	$72.0961	$72.10	$72.10	$72.10
Purchase #6	$237.49	5.707%	$251.0436	$251.04	$251.05	$251.00
Purchase #7	$87.55	13.627%	$99.4804	$99.48	$99.50	$99.50
7 purchase totals =	$1,024.96		$1,118.7944	$1,118.80	$1,118.80	$1,118.90