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	$30.34	7.148%	$32.5087	$32.51	$32.50	$32.50
Purchase #2	$242.48	7.821%	$261.4444	$261.44	$261.45	$261.40
Purchase #3	$123.37	13.419%	$139.925	$139.93	$139.95	$139.90
Purchase #4	$95.82	7.737%	$103.2336	$103.23	$103.25	$103.20
Purchase #5	$167.83	8.494%	$182.0855	$182.09	$182.10	$182.10
Purchase #6	$163.96	11.864%	$183.4122	$183.41	$183.40	$183.40
Purchase #7	$167.32	4.414%	$174.7055	$174.71	$174.70	$174.70
7 purchase totals =	$991.12		$1,077.3149	$1,077.32	$1,077.35	$1,077.20