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	$148.99	13.390%	$168.9398	$168.94	$168.95	$168.90
Purchase #2	$98.29	7.429%	$105.592	$105.59	$105.60	$105.60
Purchase #3	$167.82	10.800%	$185.9446	$185.94	$185.95	$185.90
Purchase #4	$52.94	13.236%	$59.9471	$59.95	$59.95	$59.90
Purchase #5	$167.33	4.320%	$174.5587	$174.56	$174.55	$174.60
Purchase #6	$206.40	4.648%	$215.9935	$215.99	$216.00	$216.00
Purchase #7	$192.43	11.834%	$215.2022	$215.20	$215.20	$215.20
7 purchase totals =	$1,034.20		$1,126.1779	$1,126.17	$1,126.20	$1,126.10