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	$237.37	12.576%	$267.2217	$267.22	$267.20	$267.20
Purchase #2	$248.48	10.409%	$274.3443	$274.34	$274.35	$274.30
Purchase #3	$65.71	6.374%	$69.8984	$69.90	$69.90	$69.90
Purchase #4	$159.92	4.623%	$167.3131	$167.31	$167.30	$167.30
Purchase #5	$188.58	3.348%	$194.8937	$194.89	$194.90	$194.90
Purchase #6	$98.79	12.819%	$111.4539	$111.45	$111.45	$111.50
Purchase #7	$24.86	10.295%	$27.4193	$27.42	$27.40	$27.40
7 purchase totals =	$1,023.71		$1,112.5444	$1,112.53	$1,112.50	$1,112.50