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	$205.85	13.761%	$234.177	$234.18	$234.20	$234.20
Purchase #2	$198.49	9.138%	$216.628	$216.63	$216.65	$216.60
Purchase #3	$28.48	3.635%	$29.5152	$29.52	$29.50	$29.50
Purchase #4	$59.46	10.166%	$65.5047	$65.50	$65.50	$65.50
Purchase #5	$156.94	9.382%	$171.6641	$171.66	$171.65	$171.70
Purchase #6	$108.80	6.198%	$115.5434	$115.54	$115.55	$115.50
Purchase #7	$246.93	12.791%	$278.5148	$278.51	$278.50	$278.50
7 purchase totals =	$1,004.95		$1,111.5472	$1,111.54	$1,111.55	$1,111.50