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	$212.25	9.276%	$231.9383	$231.94	$231.95	$231.90
Purchase #2	$38.46	9.861%	$42.2525	$42.25	$42.25	$42.30
Purchase #3	$40.45	4.618%	$42.318	$42.32	$42.30	$42.30
Purchase #4	$20.48	11.204%	$22.7746	$22.77	$22.75	$22.80
Purchase #5	$228.48	7.425%	$245.4446	$245.44	$245.45	$245.40
Purchase #6	$226.54	3.226%	$233.8482	$233.85	$233.85	$233.80
Purchase #7	$63.25	11.727%	$70.6673	$70.67	$70.65	$70.70
7 purchase totals =	$829.91		$889.2435	$889.24	$889.20	$889.20