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	$166.25	4.536%	$173.7911	$173.79	$173.80	$173.80
Purchase #2	$76.48	3.188%	$78.9182	$78.92	$78.90	$78.90
Purchase #3	$208.63	9.733%	$228.936	$228.94	$228.95	$228.90
Purchase #4	$130.85	9.663%	$143.494	$143.49	$143.50	$143.50
Purchase #5	$203.57	4.838%	$213.4187	$213.42	$213.40	$213.40
Purchase #6	$65.76	8.175%	$71.1359	$71.14	$71.15	$71.10
Purchase #7	$88.28	6.333%	$93.8708	$93.87	$93.85	$93.90
7 purchase totals =	$939.82		$1,003.5647	$1,003.57	$1,003.55	$1,003.50