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	$184.98	13.607%	$210.1502	$210.15	$210.15	$210.20
Purchase #2	$162.79	11.744%	$181.9081	$181.91	$181.90	$181.90
Purchase #3	$173.66	5.718%	$183.5899	$183.59	$183.60	$183.60
Purchase #4	$84.63	7.266%	$90.7792	$90.78	$90.80	$90.80
Purchase #5	$165.80	10.257%	$182.8061	$182.81	$182.80	$182.80
Purchase #6	$99.44	9.560%	$108.9465	$108.95	$108.95	$108.90
Purchase #7	$99.58	9.477%	$109.0172	$109.02	$109.00	$109.00
7 purchase totals =	$970.88		$1,067.1972	$1,067.21	$1,067.20	$1,067.20