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	$85.97	11.490%	$95.848	$95.85	$95.85	$95.80
Purchase #2	$40.72	10.219%	$44.8812	$44.88	$44.90	$44.90
Purchase #3	$151.93	7.392%	$163.1607	$163.16	$163.15	$163.20
Purchase #4	$167.33	11.256%	$186.1647	$186.16	$186.15	$186.20
Purchase #5	$96.72	3.467%	$100.0733	$100.07	$100.05	$100.10
Purchase #6	$119.29	3.361%	$123.2993	$123.30	$123.30	$123.30
Purchase #7	$148.34	13.134%	$167.823	$167.82	$167.80	$167.80
7 purchase totals =	$810.30		$881.2502	$881.24	$881.20	$881.30