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	$50.63	3.320%	$52.3109	$52.31	$52.30	$52.30
Purchase #2	$63.44	4.600%	$66.3582	$66.36	$66.35	$66.40
Purchase #3	$136.58	4.635%	$142.9105	$142.91	$142.90	$142.90
Purchase #4	$206.67	13.868%	$235.331	$235.33	$235.35	$235.30
Purchase #5	$158.86	9.128%	$173.3607	$173.36	$173.35	$173.40
Purchase #6	$224.93	13.690%	$255.7229	$255.72	$255.70	$255.70
Purchase #7	$166.32	3.626%	$172.3508	$172.35	$172.35	$172.40
7 purchase totals =	$1,007.43		$1,098.3450	$1,098.34	$1,098.30	$1,098.40