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	$139.37	3.809%	$144.6786	$144.68	$144.70	$144.70
Purchase #2	$78.58	5.168%	$82.641	$82.64	$82.65	$82.60
Purchase #3	$186.93	11.400%	$208.24	$208.24	$208.25	$208.20
Purchase #4	$90.89	11.763%	$101.5814	$101.58	$101.60	$101.60
Purchase #5	$75.76	10.786%	$83.9315	$83.93	$83.95	$83.90
Purchase #6	$191.27	12.617%	$215.4025	$215.40	$215.40	$215.40
Purchase #7	$210.51	8.512%	$228.4286	$228.43	$228.45	$228.40
7 purchase totals =	$973.31		$1,064.9036	$1,064.90	$1,065.00	$1,064.80