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	$67.56	6.180%	$71.7352	$71.74	$71.75	$71.70
Purchase #2	$71.40	9.266%	$78.0159	$78.02	$78.00	$78.00
Purchase #3	$90.93	11.754%	$101.6179	$101.62	$101.60	$101.60
Purchase #4	$63.78	3.264%	$65.8618	$65.86	$65.85	$65.90
Purchase #5	$105.87	10.418%	$116.8995	$116.90	$116.90	$116.90
Purchase #6	$220.27	5.674%	$232.7681	$232.77	$232.75	$232.80
Purchase #7	$144.40	12.422%	$162.3374	$162.34	$162.35	$162.30
7 purchase totals =	$764.21		$829.2358	$829.25	$829.20	$829.20