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	$247.69	13.782%	$281.8266	$281.83	$281.85	$281.80
Purchase #2	$146.36	9.521%	$160.2949	$160.29	$160.30	$160.30
Purchase #3	$32.90	8.277%	$35.6231	$35.62	$35.60	$35.60
Purchase #4	$43.59	4.566%	$45.5803	$45.58	$45.60	$45.60
Purchase #5	$205.68	9.589%	$225.4027	$225.40	$225.40	$225.40
Purchase #6	$147.55	12.782%	$166.4098	$166.41	$166.40	$166.40
Purchase #7	$136.70	9.339%	$149.4664	$149.47	$149.45	$149.50
7 purchase totals =	$960.47		$1,064.6038	$1,064.60	$1,064.60	$1,064.60