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	$42.59	11.378%	$47.4359	$47.44	$47.45	$47.40
Purchase #2	$76.48	11.561%	$85.3219	$85.32	$85.30	$85.30
Purchase #3	$63.70	3.221%	$65.7518	$65.75	$65.75	$65.80
Purchase #4	$173.98	7.133%	$186.39	$186.39	$186.40	$186.40
Purchase #5	$75.60	6.459%	$80.483	$80.48	$80.50	$80.50
Purchase #6	$233.52	4.671%	$244.4277	$244.43	$244.45	$244.40
Purchase #7	$128.69	8.653%	$139.8255	$139.83	$139.85	$139.80
7 purchase totals =	$794.56		$849.6358	$849.64	$849.70	$849.60