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	$65.58	4.576%	$68.5809	$68.58	$68.60	$68.60
Purchase #2	$247.80	7.860%	$267.2771	$267.28	$267.30	$267.30
Purchase #3	$160.55	13.475%	$182.1841	$182.18	$182.20	$182.20
Purchase #4	$94.82	9.143%	$103.4894	$103.49	$103.50	$103.50
Purchase #5	$191.47	3.681%	$198.518	$198.52	$198.50	$198.50
Purchase #6	$100.94	8.849%	$109.8722	$109.87	$109.85	$109.90
Purchase #7	$82.30	3.310%	$85.0241	$85.02	$85.00	$85.00
7 purchase totals =	$943.46		$1,014.9458	$1,014.94	$1,014.95	$1,015.00