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	$210.34	4.370%	$219.5319	$219.53	$219.55	$219.50
Purchase #2	$27.92	4.185%	$29.0885	$29.09	$29.10	$29.10
Purchase #3	$88.98	13.306%	$100.8197	$100.82	$100.80	$100.80
Purchase #4	$126.66	5.386%	$133.4819	$133.48	$133.50	$133.50
Purchase #5	$170.83	6.228%	$181.4693	$181.47	$181.45	$181.50
Purchase #6	$35.97	13.852%	$40.9526	$40.95	$40.95	$41.00
Purchase #7	$139.71	11.742%	$156.1147	$156.11	$156.10	$156.10
7 purchase totals =	$800.41		$861.4586	$861.45	$861.45	$861.50