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	$208.25	6.827%	$222.4672	$222.47	$222.45	$222.50
Purchase #2	$52.38	4.629%	$54.8047	$54.80	$54.80	$54.80
Purchase #3	$190.34	7.111%	$203.8751	$203.88	$203.90	$203.90
Purchase #4	$237.49	9.417%	$259.8544	$259.85	$259.85	$259.90
Purchase #5	$172.90	8.357%	$187.3493	$187.35	$187.35	$187.30
Purchase #6	$65.49	11.430%	$72.9755	$72.98	$73.00	$73.00
Purchase #7	$205.32	3.174%	$211.8369	$211.84	$211.85	$211.80
7 purchase totals =	$1,132.17		$1,213.1631	$1,213.17	$1,213.20	$1,213.20