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	$184.73	8.191%	$199.8612	$199.86	$199.85	$199.90
Purchase #2	$171.84	4.664%	$179.8546	$179.85	$179.85	$179.90
Purchase #3	$173.31	10.262%	$191.0951	$191.10	$191.10	$191.10
Purchase #4	$230.56	11.831%	$257.8376	$257.84	$257.85	$257.80
Purchase #5	$167.80	3.435%	$173.5639	$173.56	$173.55	$173.60
Purchase #6	$155.90	3.227%	$160.9309	$160.93	$160.95	$160.90
Purchase #7	$40.39	12.774%	$45.5494	$45.55	$45.55	$45.50
7 purchase totals =	$1,124.53		$1,208.6927	$1,208.69	$1,208.70	$1,208.70