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	$133.42	12.697%	$150.3603	$150.36	$150.35	$150.40
Purchase #2	$24.74	10.375%	$27.3068	$27.31	$27.30	$27.30
Purchase #3	$64.40	12.528%	$72.468	$72.47	$72.45	$72.50
Purchase #4	$206.41	6.797%	$220.4397	$220.44	$220.45	$220.40
Purchase #5	$192.40	3.140%	$198.4414	$198.44	$198.45	$198.40
Purchase #6	$116.89	6.404%	$124.3756	$124.38	$124.40	$124.40
Purchase #7	$198.66	9.436%	$217.4056	$217.41	$217.40	$217.40
7 purchase totals =	$936.92		$1,010.7974	$1,010.81	$1,010.80	$1,010.80