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	$174.46	6.172%	$185.2277	$185.23	$185.25	$185.20
Purchase #2	$33.30	6.539%	$35.4775	$35.48	$35.50	$35.50
Purchase #3	$19.89	5.560%	$20.9959	$21.00	$21.00	$21.00
Purchase #4	$224.31	8.594%	$243.5872	$243.59	$243.60	$243.60
Purchase #5	$227.42	4.669%	$238.0382	$238.04	$238.05	$238.00
Purchase #6	$53.44	8.543%	$58.0054	$58.01	$58.00	$58.00
Purchase #7	$165.41	13.658%	$188.0017	$188.00	$188.00	$188.00
7 purchase totals =	$898.23		$969.3336	$969.35	$969.40	$969.30