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	$229.64	5.412%	$242.0681	$242.07	$242.05	$242.10
Purchase #2	$52.87	5.812%	$55.9428	$55.94	$55.95	$55.90
Purchase #3	$67.55	3.495%	$69.9109	$69.91	$69.90	$69.90
Purchase #4	$77.56	10.284%	$85.5363	$85.54	$85.55	$85.50
Purchase #5	$99.28	9.287%	$108.5001	$108.50	$108.50	$108.50
Purchase #6	$90.37	11.698%	$100.9415	$100.94	$100.95	$100.90
Purchase #7	$190.91	12.549%	$214.8673	$214.87	$214.85	$214.90
7 purchase totals =	$808.18		$877.7670	$877.77	$877.75	$877.70