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	$102.78	4.668%	$107.5778	$107.58	$107.60	$107.60
Purchase #2	$94.33	8.705%	$102.5414	$102.54	$102.55	$102.50
Purchase #3	$104.83	11.137%	$116.5049	$116.50	$116.50	$116.50
Purchase #4	$125.82	11.473%	$140.2553	$140.26	$140.25	$140.30
Purchase #5	$100.77	10.279%	$111.1281	$111.13	$111.15	$111.10
Purchase #6	$33.50	4.606%	$35.043	$35.04	$35.05	$35.00
Purchase #7	$102.46	8.813%	$111.4898	$111.49	$111.50	$111.50
7 purchase totals =	$664.49		$724.5403	$724.54	$724.60	$724.50