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	$152.92	5.683%	$161.6104	$161.61	$161.60	$161.60
Purchase #2	$94.66	9.470%	$103.6243	$103.62	$103.60	$103.60
Purchase #3	$86.63	9.836%	$95.1509	$95.15	$95.15	$95.20
Purchase #4	$13.71	11.240%	$15.251	$15.25	$15.25	$15.30
Purchase #5	$32.72	8.842%	$35.6131	$35.61	$35.60	$35.60
Purchase #6	$25.83	12.684%	$29.1063	$29.11	$29.10	$29.10
Purchase #7	$179.26	3.286%	$185.1505	$185.15	$185.15	$185.20
7 purchase totals =	$585.73		$625.5065	$625.50	$625.45	$625.60