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	$87.81	7.788%	$94.6486	$94.65	$94.65	$94.60
Purchase #2	$145.57	12.762%	$164.1476	$164.15	$164.15	$164.10
Purchase #3	$231.55	5.382%	$244.012	$244.01	$244.00	$244.00
Purchase #4	$150.84	3.266%	$155.7664	$155.77	$155.75	$155.80
Purchase #5	$167.65	10.523%	$185.2918	$185.29	$185.30	$185.30
Purchase #6	$166.92	10.646%	$184.6903	$184.69	$184.70	$184.70
Purchase #7	$93.48	7.417%	$100.4134	$100.41	$100.40	$100.40
7 purchase totals =	$1,043.82		$1,128.9701	$1,128.97	$1,128.95	$1,128.90