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	$37.61	9.759%	$41.2804	$41.28	$41.30	$41.30
Purchase #2	$182.38	7.386%	$195.8506	$195.85	$195.85	$195.90
Purchase #3	$60.81	10.248%	$67.0418	$67.04	$67.05	$67.00
Purchase #4	$89.66	12.559%	$100.9204	$100.92	$100.90	$100.90
Purchase #5	$54.94	5.517%	$57.971	$57.97	$57.95	$58.00
Purchase #6	$204.89	5.379%	$215.911	$215.91	$215.90	$215.90
Purchase #7	$59.46	9.566%	$65.1479	$65.15	$65.15	$65.10
7 purchase totals =	$689.75		$744.1231	$744.12	$744.10	$744.10