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	$60.50	10.200%	$66.671	$66.67	$66.65	$66.70
Purchase #2	$98.30	13.728%	$111.7946	$111.79	$111.80	$111.80
Purchase #3	$74.26	11.660%	$82.9187	$82.92	$82.90	$82.90
Purchase #4	$86.98	3.273%	$89.8269	$89.83	$89.85	$89.80
Purchase #5	$30.91	8.409%	$33.5092	$33.51	$33.50	$33.50
Purchase #6	$42.79	10.597%	$47.3245	$47.32	$47.30	$47.30
Purchase #7	$27.75	13.650%	$31.5379	$31.54	$31.55	$31.50
7 purchase totals =	$421.49		$463.5828	$463.58	$463.55	$463.50