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	$117.60	11.839%	$131.5227	$131.52	$131.50	$131.50
Purchase #2	$31.75	8.722%	$34.5192	$34.52	$34.50	$34.50
Purchase #3	$90.68	3.418%	$93.7794	$93.78	$93.80	$93.80
Purchase #4	$97.68	6.605%	$104.1318	$104.13	$104.15	$104.10
Purchase #5	$38.31	11.360%	$42.662	$42.66	$42.65	$42.70
Purchase #6	$249.43	9.826%	$273.939	$273.94	$273.95	$273.90
Purchase #7	$89.56	12.297%	$100.5732	$100.57	$100.55	$100.60
7 purchase totals =	$715.01		$781.1273	$781.12	$781.10	$781.10