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	$32.46	10.669%	$35.9232	$35.92	$35.90	$35.90
Purchase #2	$95.33	11.176%	$105.9841	$105.98	$106.00	$106.00
Purchase #3	$210.69	5.768%	$222.8426	$222.84	$222.85	$222.80
Purchase #4	$83.97	6.598%	$89.5103	$89.51	$89.50	$89.50
Purchase #5	$211.92	3.779%	$219.9285	$219.93	$219.95	$219.90
Purchase #6	$133.30	10.310%	$147.0432	$147.04	$147.05	$147.00
Purchase #7	$25.85	13.396%	$29.3129	$29.31	$29.30	$29.30
7 purchase totals =	$793.52		$850.5448	$850.53	$850.55	$850.40