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	$146.48	10.616%	$162.0303	$162.03	$162.05	$162.00
Purchase #2	$200.93	11.352%	$223.7396	$223.74	$223.75	$223.70
Purchase #3	$36.51	13.831%	$41.5597	$41.56	$41.55	$41.60
Purchase #4	$36.61	10.516%	$40.4599	$40.46	$40.45	$40.50
Purchase #5	$63.27	11.266%	$70.398	$70.40	$70.40	$70.40
Purchase #6	$126.31	4.320%	$131.7666	$131.77	$131.75	$131.80
Purchase #7	$203.92	11.629%	$227.6339	$227.63	$227.65	$227.60
7 purchase totals =	$814.03		$897.5880	$897.59	$897.60	$897.60