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	$61.96	6.364%	$65.9031	$65.90	$65.90	$65.90
Purchase #2	$85.99	4.543%	$89.8965	$89.90	$89.90	$89.90
Purchase #3	$173.90	6.257%	$184.7809	$184.78	$184.80	$184.80
Purchase #4	$193.59	11.375%	$215.6109	$215.61	$215.60	$215.60
Purchase #5	$118.45	5.703%	$125.2052	$125.21	$125.20	$125.20
Purchase #6	$239.36	12.648%	$269.6343	$269.63	$269.65	$269.60
Purchase #7	$24.31	12.733%	$27.4054	$27.41	$27.40	$27.40
7 purchase totals =	$897.56		$978.4363	$978.44	$978.45	$978.40