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	$127.45	10.322%	$140.6054	$140.61	$140.60	$140.60
Purchase #2	$164.93	12.850%	$186.1235	$186.12	$186.10	$186.10
Purchase #3	$136.71	10.800%	$151.4747	$151.47	$151.45	$151.50
Purchase #4	$29.55	10.312%	$32.5972	$32.60	$32.60	$32.60
Purchase #5	$180.54	8.788%	$196.4059	$196.41	$196.40	$196.40
Purchase #6	$67.87	12.259%	$76.1902	$76.19	$76.20	$76.20
Purchase #7	$59.38	9.275%	$64.8875	$64.89	$64.90	$64.90
7 purchase totals =	$766.43		$848.2844	$848.29	$848.25	$848.30