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	$10.41	4.517%	$10.8802	$10.88	$10.90	$10.90
Purchase #2	$9.54	4.429%	$9.9625	$9.96	$9.95	$10.00
Purchase #3	$31.58	13.467%	$35.8329	$35.83	$35.85	$35.80
Purchase #4	$99.48	6.821%	$106.2655	$106.27	$106.25	$106.30
Purchase #5	$178.87	3.480%	$185.0947	$185.09	$185.10	$185.10
Purchase #6	$25.64	10.319%	$28.2858	$28.29	$28.30	$28.30
Purchase #7	$90.39	4.309%	$94.2849	$94.28	$94.30	$94.30
7 purchase totals =	$445.91		$470.6065	$470.60	$470.65	$470.70