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	$126.88	5.303%	$133.6084	$133.61	$133.60	$133.60
Purchase #2	$85.65	11.607%	$95.5914	$95.59	$95.60	$95.60
Purchase #3	$205.83	3.338%	$212.7006	$212.70	$212.70	$212.70
Purchase #4	$137.44	9.726%	$150.8074	$150.81	$150.80	$150.80
Purchase #5	$97.83	5.404%	$103.1167	$103.12	$103.10	$103.10
Purchase #6	$127.34	13.655%	$144.7283	$144.73	$144.75	$144.70
Purchase #7	$244.71	6.281%	$260.0802	$260.08	$260.10	$260.10
7 purchase totals =	$1,025.68		$1,100.6330	$1,100.64	$1,100.65	$1,100.60