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	$98.38	3.531%	$101.8538	$101.85	$101.85	$101.90
Purchase #2	$109.56	5.789%	$115.9024	$115.90	$115.90	$115.90
Purchase #3	$78.27	8.598%	$84.9997	$85.00	$85.00	$85.00
Purchase #4	$208.49	6.471%	$221.9814	$221.98	$222.00	$222.00
Purchase #5	$94.49	6.774%	$100.8908	$100.89	$100.90	$100.90
Purchase #6	$230.80	11.518%	$257.3835	$257.38	$257.40	$257.40
Purchase #7	$106.77	6.181%	$113.3695	$113.37	$113.35	$113.40
7 purchase totals =	$926.76		$996.3811	$996.37	$996.40	$996.50