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	$135.59	4.551%	$141.7607	$141.76	$141.75	$141.80
Purchase #2	$153.97	3.256%	$158.9833	$158.98	$159.00	$159.00
Purchase #3	$71.87	8.544%	$78.0106	$78.01	$78.00	$78.00
Purchase #4	$27.85	12.847%	$31.4279	$31.43	$31.45	$31.40
Purchase #5	$82.75	9.188%	$90.3531	$90.35	$90.35	$90.40
Purchase #6	$249.42	8.710%	$271.1445	$271.14	$271.15	$271.10
Purchase #7	$41.69	8.698%	$45.3162	$45.32	$45.30	$45.30
7 purchase totals =	$763.14		$816.9963	$816.99	$817.00	$817.00