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	$233.53	4.108%	$243.1234	$243.12	$243.10	$243.10
Purchase #2	$101.75	10.416%	$112.3483	$112.35	$112.35	$112.30
Purchase #3	$142.85	5.664%	$150.941	$150.94	$150.95	$150.90
Purchase #4	$52.50	11.447%	$58.5097	$58.51	$58.50	$58.50
Purchase #5	$49.64	13.577%	$56.3796	$56.38	$56.40	$56.40
Purchase #6	$130.94	13.393%	$148.4768	$148.48	$148.50	$148.50
Purchase #7	$172.33	11.846%	$192.7442	$192.74	$192.75	$192.70
7 purchase totals =	$883.54		$962.5230	$962.52	$962.55	$962.40