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	$58.71	4.307%	$61.2386	$61.24	$61.25	$61.20
Purchase #2	$33.25	6.706%	$35.4797	$35.48	$35.50	$35.50
Purchase #3	$133.53	9.837%	$146.6653	$146.67	$146.65	$146.70
Purchase #4	$82.67	4.521%	$86.4075	$86.41	$86.40	$86.40
Purchase #5	$112.31	4.246%	$117.0787	$117.08	$117.10	$117.10
Purchase #6	$31.89	5.557%	$33.6621	$33.66	$33.65	$33.70
Purchase #7	$151.95	13.734%	$172.8188	$172.82	$172.80	$172.80
7 purchase totals =	$604.31		$653.3507	$653.36	$653.35	$653.40