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	$9.44	13.704%	$10.7337	$10.73	$10.75	$10.70
Purchase #2	$69.39	12.181%	$77.8424	$77.84	$77.85	$77.80
Purchase #3	$137.85	13.353%	$156.2571	$156.26	$156.25	$156.30
Purchase #4	$85.26	6.250%	$90.5888	$90.59	$90.60	$90.60
Purchase #5	$120.55	5.274%	$126.9078	$126.91	$126.90	$126.90
Purchase #6	$204.83	5.187%	$215.4545	$215.45	$215.45	$215.50
Purchase #7	$57.93	8.321%	$62.7504	$62.75	$62.75	$62.80
7 purchase totals =	$685.25		$740.5347	$740.53	$740.55	$740.60