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	$154.73	7.476%	$166.2976	$166.30	$166.30	$166.30
Purchase #2	$126.66	13.263%	$143.4589	$143.46	$143.45	$143.50
Purchase #3	$75.92	13.136%	$85.8929	$85.89	$85.90	$85.90
Purchase #4	$83.90	7.568%	$90.2496	$90.25	$90.25	$90.20
Purchase #5	$82.76	13.167%	$93.657	$93.66	$93.65	$93.70
Purchase #6	$112.32	7.136%	$120.3352	$120.34	$120.35	$120.30
Purchase #7	$166.34	6.314%	$176.8427	$176.84	$176.85	$176.80
7 purchase totals =	$802.63		$876.7339	$876.74	$876.75	$876.70