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	$220.55	12.830%	$248.8466	$248.85	$248.85	$248.80
Purchase #2	$18.58	12.202%	$20.8471	$20.85	$20.85	$20.80
Purchase #3	$110.37	12.257%	$123.8981	$123.90	$123.90	$123.90
Purchase #4	$171.56	7.739%	$184.837	$184.84	$184.85	$184.80
Purchase #5	$191.81	10.671%	$212.278	$212.28	$212.30	$212.30
Purchase #6	$95.87	9.522%	$104.9987	$105.00	$105.00	$105.00
Purchase #7	$171.49	5.401%	$180.7522	$180.75	$180.75	$180.80
7 purchase totals =	$980.23		$1,076.4577	$1,076.47	$1,076.50	$1,076.40