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	$46.53	7.140%	$49.8522	$49.85	$49.85	$49.90
Purchase #2	$116.93	9.254%	$127.7507	$127.75	$127.75	$127.80
Purchase #3	$38.82	3.452%	$40.1601	$40.16	$40.15	$40.20
Purchase #4	$140.41	8.845%	$152.8293	$152.83	$152.85	$152.80
Purchase #5	$244.57	11.279%	$272.1551	$272.16	$272.15	$272.20
Purchase #6	$191.30	12.559%	$215.3254	$215.33	$215.35	$215.30
Purchase #7	$5.83	7.544%	$6.2698	$6.27	$6.25	$6.30
7 purchase totals =	$784.39		$864.3426	$864.35	$864.35	$864.50