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	$163.29	13.283%	$184.9798	$184.98	$185.00	$185.00
Purchase #2	$234.57	4.645%	$245.4658	$245.47	$245.45	$245.50
Purchase #3	$197.59	10.524%	$218.3844	$218.38	$218.40	$218.40
Purchase #4	$151.32	6.833%	$161.6597	$161.66	$161.65	$161.70
Purchase #5	$42.60	4.147%	$44.3666	$44.37	$44.35	$44.40
Purchase #6	$129.54	11.287%	$144.1612	$144.16	$144.15	$144.20
Purchase #7	$61.83	9.304%	$67.5827	$67.58	$67.60	$67.60
7 purchase totals =	$980.74		$1,066.6002	$1,066.60	$1,066.60	$1,066.80