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	$164.76	11.426%	$183.5855	$183.59	$183.60	$183.60
Purchase #2	$7.49	4.758%	$7.8464	$7.85	$7.85	$7.80
Purchase #3	$233.65	5.583%	$246.6947	$246.69	$246.70	$246.70
Purchase #4	$78.52	5.463%	$82.8095	$82.81	$82.80	$82.80
Purchase #5	$179.50	8.367%	$194.5188	$194.52	$194.50	$194.50
Purchase #6	$38.56	9.119%	$42.0763	$42.08	$42.10	$42.10
Purchase #7	$92.83	5.420%	$97.8614	$97.86	$97.85	$97.90
7 purchase totals =	$795.31		$855.3926	$855.40	$855.40	$855.40