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	$169.92	9.393%	$185.8806	$185.88	$185.90	$185.90
Purchase #2	$9.32	11.535%	$10.3951	$10.40	$10.40	$10.40
Purchase #3	$74.69	10.299%	$82.3823	$82.38	$82.40	$82.40
Purchase #4	$113.89	10.833%	$126.2277	$126.23	$126.25	$126.20
Purchase #5	$195.67	13.715%	$222.5061	$222.51	$222.50	$222.50
Purchase #6	$136.46	7.169%	$146.2428	$146.24	$146.25	$146.20
Purchase #7	$113.39	12.691%	$127.7803	$127.78	$127.80	$127.80
7 purchase totals =	$813.34		$901.4149	$901.42	$901.50	$901.40