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	$76.26	3.503%	$78.9314	$78.93	$78.95	$78.90
Purchase #2	$228.69	12.328%	$256.8829	$256.88	$256.90	$256.90
Purchase #3	$219.30	13.712%	$249.3704	$249.37	$249.35	$249.40
Purchase #4	$66.97	7.569%	$72.039	$72.04	$72.05	$72.00
Purchase #5	$204.61	10.155%	$225.3881	$225.39	$225.40	$225.40
Purchase #6	$175.94	13.867%	$200.3376	$200.34	$200.35	$200.30
Purchase #7	$11.57	9.265%	$12.642	$12.64	$12.65	$12.60
7 purchase totals =	$983.34		$1,095.5914	$1,095.59	$1,095.65	$1,095.50