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	$185.86	13.204%	$210.401	$210.40	$210.40	$210.40
Purchase #2	$23.71	8.626%	$25.7552	$25.76	$25.75	$25.80
Purchase #3	$53.35	11.137%	$59.2916	$59.29	$59.30	$59.30
Purchase #4	$241.60	10.341%	$266.5839	$266.58	$266.60	$266.60
Purchase #5	$111.57	6.718%	$119.0653	$119.07	$119.05	$119.10
Purchase #6	$149.95	6.721%	$160.0281	$160.03	$160.05	$160.00
Purchase #7	$218.92	11.583%	$244.2775	$244.28	$244.30	$244.30
7 purchase totals =	$984.96		$1,085.4026	$1,085.41	$1,085.45	$1,085.50