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	$206.42	10.370%	$227.8258	$227.83	$227.85	$227.80
Purchase #2	$207.34	13.750%	$235.8493	$235.85	$235.85	$235.80
Purchase #3	$229.76	13.291%	$260.2974	$260.30	$260.30	$260.30
Purchase #4	$52.69	12.321%	$59.1819	$59.18	$59.20	$59.20
Purchase #5	$58.79	5.196%	$61.8447	$61.84	$61.85	$61.80
Purchase #6	$57.80	8.334%	$62.6171	$62.62	$62.60	$62.60
Purchase #7	$174.63	4.759%	$182.9406	$182.94	$182.95	$182.90
7 purchase totals =	$987.43		$1,090.5568	$1,090.56	$1,090.60	$1,090.40