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	$69.84	3.873%	$72.5449	$72.54	$72.55	$72.50
Purchase #2	$65.90	9.534%	$72.1829	$72.18	$72.20	$72.20
Purchase #3	$130.64	8.490%	$141.7313	$141.73	$141.75	$141.70
Purchase #4	$77.98	5.601%	$82.3477	$82.35	$82.35	$82.30
Purchase #5	$49.59	9.397%	$54.25	$54.25	$54.25	$54.30
Purchase #6	$114.57	10.570%	$126.68	$126.68	$126.70	$126.70
Purchase #7	$77.76	10.225%	$85.711	$85.71	$85.70	$85.70
7 purchase totals =	$586.28		$635.4478	$635.44	$635.50	$635.40