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	$218.34	7.440%	$234.5845	$234.58	$234.60	$234.60
Purchase #2	$118.31	7.833%	$127.5772	$127.58	$127.60	$127.60
Purchase #3	$62.53	4.355%	$65.2532	$65.25	$65.25	$65.30
Purchase #4	$98.27	8.741%	$106.8598	$106.86	$106.85	$106.90
Purchase #5	$14.53	9.485%	$15.9082	$15.91	$15.90	$15.90
Purchase #6	$162.65	12.196%	$182.4868	$182.49	$182.50	$182.50
Purchase #7	$100.48	12.328%	$112.8672	$112.87	$112.85	$112.90
7 purchase totals =	$775.11		$845.5369	$845.54	$845.55	$845.70