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	$43.95	5.669%	$46.4415	$46.44	$46.45	$46.40
Purchase #2	$61.32	10.556%	$67.7929	$67.79	$67.80	$67.80
Purchase #3	$220.94	7.330%	$237.1349	$237.13	$237.15	$237.10
Purchase #4	$41.34	9.109%	$45.1057	$45.11	$45.10	$45.10
Purchase #5	$224.90	13.722%	$255.7608	$255.76	$255.75	$255.80
Purchase #6	$82.32	12.665%	$92.7458	$92.75	$92.75	$92.70
Purchase #7	$126.66	3.288%	$130.8246	$130.82	$130.80	$130.80
7 purchase totals =	$801.43		$875.8062	$875.80	$875.80	$875.70