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	$71.45	4.770%	$74.8582	$74.86	$74.85	$74.90
Purchase #2	$146.33	13.654%	$166.3099	$166.31	$166.30	$166.30
Purchase #3	$145.55	3.105%	$150.0693	$150.07	$150.05	$150.10
Purchase #4	$67.66	6.712%	$72.2013	$72.20	$72.20	$72.20
Purchase #5	$133.94	7.354%	$143.7899	$143.79	$143.80	$143.80
Purchase #6	$210.75	5.301%	$221.9219	$221.92	$221.90	$221.90
Purchase #7	$89.47	5.825%	$94.6816	$94.68	$94.70	$94.70
7 purchase totals =	$865.15		$923.8321	$923.83	$923.80	$923.90