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	$163.91	12.815%	$184.9151	$184.92	$184.90	$184.90
Purchase #2	$123.96	7.567%	$133.3401	$133.34	$133.35	$133.30
Purchase #3	$112.48	10.516%	$124.3084	$124.31	$124.30	$124.30
Purchase #4	$238.43	5.238%	$250.919	$250.92	$250.90	$250.90
Purchase #5	$134.33	10.848%	$148.9021	$148.90	$148.90	$148.90
Purchase #6	$65.29	8.804%	$71.0381	$71.04	$71.05	$71.00
Purchase #7	$173.86	4.448%	$181.5933	$181.59	$181.60	$181.60
7 purchase totals =	$1,012.26		$1,095.0161	$1,095.02	$1,095.00	$1,094.90