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	$157.95	6.697%	$168.5279	$168.53	$168.55	$168.50
Purchase #2	$54.46	6.279%	$57.8795	$57.88	$57.90	$57.90
Purchase #3	$26.42	5.557%	$27.8882	$27.89	$27.90	$27.90
Purchase #4	$66.37	9.785%	$72.8643	$72.86	$72.85	$72.90
Purchase #5	$114.30	3.789%	$118.6308	$118.63	$118.65	$118.60
Purchase #6	$92.60	3.387%	$95.7364	$95.74	$95.75	$95.70
Purchase #7	$213.49	3.863%	$221.7371	$221.74	$221.75	$221.70
7 purchase totals =	$725.59		$763.2642	$763.27	$763.35	$763.20