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	$231.30	13.429%	$262.3613	$262.36	$262.35	$262.40
Purchase #2	$103.28	5.449%	$108.9077	$108.91	$108.90	$108.90
Purchase #3	$188.33	6.596%	$200.7522	$200.75	$200.75	$200.80
Purchase #4	$15.25	4.308%	$15.907	$15.91	$15.90	$15.90
Purchase #5	$32.69	7.545%	$35.1565	$35.16	$35.15	$35.20
Purchase #6	$144.95	13.774%	$164.9154	$164.92	$164.90	$164.90
Purchase #7	$109.28	6.686%	$116.5865	$116.59	$116.60	$116.60
7 purchase totals =	$825.08		$904.5866	$904.60	$904.55	$904.70