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	$238.60	12.250%	$267.8285	$267.83	$267.85	$267.80
Purchase #2	$63.55	13.432%	$72.086	$72.09	$72.10	$72.10
Purchase #3	$85.54	5.789%	$90.4919	$90.49	$90.50	$90.50
Purchase #4	$36.26	11.748%	$40.5198	$40.52	$40.50	$40.50
Purchase #5	$225.68	12.405%	$253.6756	$253.68	$253.70	$253.70
Purchase #6	$137.85	13.172%	$156.0076	$156.01	$156.00	$156.00
Purchase #7	$248.98	6.410%	$264.9396	$264.94	$264.95	$264.90
7 purchase totals =	$1,036.46		$1,145.5490	$1,145.56	$1,145.60	$1,145.50