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	$146.55	12.405%	$164.7295	$164.73	$164.75	$164.70
Purchase #2	$215.91	8.481%	$234.2213	$234.22	$234.20	$234.20
Purchase #3	$179.32	9.309%	$196.0129	$196.01	$196.00	$196.00
Purchase #4	$69.96	12.779%	$78.9002	$78.90	$78.90	$78.90
Purchase #5	$201.47	7.151%	$215.8771	$215.88	$215.90	$215.90
Purchase #6	$144.73	7.113%	$155.0246	$155.02	$155.00	$155.00
Purchase #7	$63.53	6.428%	$67.6137	$67.61	$67.60	$67.60
7 purchase totals =	$1,021.47		$1,112.3793	$1,112.37	$1,112.35	$1,112.30