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	$18.25	4.139%	$19.0054	$19.01	$19.00	$19.00
Purchase #2	$89.49	4.452%	$93.4741	$93.47	$93.45	$93.50
Purchase #3	$37.83	10.159%	$41.6731	$41.67	$41.65	$41.70
Purchase #4	$219.86	13.171%	$248.8178	$248.82	$248.80	$248.80
Purchase #5	$120.39	6.264%	$127.9312	$127.93	$127.95	$127.90
Purchase #6	$60.33	4.872%	$63.2693	$63.27	$63.25	$63.30
Purchase #7	$103.66	9.305%	$113.3056	$113.31	$113.30	$113.30
7 purchase totals =	$649.81		$707.4765	$707.48	$707.40	$707.50