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	$198.99	4.569%	$208.0819	$208.08	$208.10	$208.10
Purchase #2	$62.72	7.514%	$67.4328	$67.43	$67.45	$67.40
Purchase #3	$243.87	11.443%	$271.776	$271.78	$271.80	$271.80
Purchase #4	$184.73	13.847%	$210.3096	$210.31	$210.30	$210.30
Purchase #5	$36.72	4.345%	$38.3155	$38.32	$38.30	$38.30
Purchase #6	$91.47	11.312%	$101.8171	$101.82	$101.80	$101.80
Purchase #7	$67.44	8.645%	$73.2702	$73.27	$73.25	$73.30
7 purchase totals =	$885.94		$971.0031	$971.01	$971.00	$971.00