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	$118.63	6.117%	$125.8866	$125.89	$125.90	$125.90
Purchase #2	$237.94	9.308%	$260.0875	$260.09	$260.10	$260.10
Purchase #3	$126.78	3.259%	$130.9118	$130.91	$130.90	$130.90
Purchase #4	$75.60	10.435%	$83.4889	$83.49	$83.50	$83.50
Purchase #5	$76.89	7.717%	$82.8236	$82.82	$82.80	$82.80
Purchase #6	$79.32	5.798%	$83.919	$83.92	$83.90	$83.90
Purchase #7	$53.78	9.257%	$58.7584	$58.76	$58.75	$58.80
7 purchase totals =	$768.94		$825.8758	$825.88	$825.85	$825.90