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	$76.32	12.132%	$85.5791	$85.58	$85.60	$85.60
Purchase #2	$78.54	11.104%	$87.2611	$87.26	$87.25	$87.30
Purchase #3	$192.26	7.163%	$206.0316	$206.03	$206.05	$206.00
Purchase #4	$98.95	5.357%	$104.2508	$104.25	$104.25	$104.30
Purchase #5	$140.43	7.444%	$150.8836	$150.88	$150.90	$150.90
Purchase #6	$128.57	11.114%	$142.8593	$142.86	$142.85	$142.90
Purchase #7	$241.85	9.518%	$264.8693	$264.87	$264.85	$264.90
7 purchase totals =	$956.92		$1,041.7348	$1,041.73	$1,041.75	$1,041.90