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	$173.32	13.565%	$196.8309	$196.83	$196.85	$196.80
Purchase #2	$102.53	6.126%	$108.811	$108.81	$108.80	$108.80
Purchase #3	$245.31	7.554%	$263.8407	$263.84	$263.85	$263.80
Purchase #4	$75.33	10.628%	$83.3361	$83.34	$83.35	$83.30
Purchase #5	$78.84	10.293%	$86.955	$86.96	$86.95	$87.00
Purchase #6	$30.78	7.135%	$32.9762	$32.98	$33.00	$33.00
Purchase #7	$232.51	12.786%	$262.2387	$262.24	$262.25	$262.20
7 purchase totals =	$938.62		$1,034.9886	$1,035.00	$1,035.05	$1,034.90