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	$189.90	3.150%	$195.8819	$195.88	$195.90	$195.90
Purchase #2	$40.41	5.815%	$42.7598	$42.76	$42.75	$42.80
Purchase #3	$53.53	4.738%	$56.0663	$56.07	$56.05	$56.10
Purchase #4	$143.64	4.826%	$150.5721	$150.57	$150.55	$150.60
Purchase #5	$224.53	10.574%	$248.2718	$248.27	$248.25	$248.30
Purchase #6	$76.45	9.622%	$83.806	$83.81	$83.80	$83.80
Purchase #7	$183.46	6.819%	$195.9701	$195.97	$195.95	$196.00
7 purchase totals =	$911.92		$973.3280	$973.33	$973.25	$973.50