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	$125.63	13.766%	$142.9242	$142.92	$142.90	$142.90
Purchase #2	$209.94	9.865%	$230.6506	$230.65	$230.65	$230.70
Purchase #3	$140.35	8.755%	$152.6376	$152.64	$152.65	$152.60
Purchase #4	$63.68	8.828%	$69.3017	$69.30	$69.30	$69.30
Purchase #5	$148.71	13.345%	$168.5553	$168.56	$168.55	$168.60
Purchase #6	$237.95	7.282%	$255.2775	$255.28	$255.30	$255.30
Purchase #7	$72.64	8.141%	$78.5536	$78.55	$78.55	$78.60
7 purchase totals =	$998.90		$1,097.9005	$1,097.90	$1,097.90	$1,098.00