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	$77.81	11.618%	$86.85	$86.85	$86.85	$86.90
Purchase #2	$205.64	4.761%	$215.4305	$215.43	$215.45	$215.40
Purchase #3	$34.91	11.184%	$38.8143	$38.81	$38.80	$38.80
Purchase #4	$59.85	11.794%	$66.9087	$66.91	$66.90	$66.90
Purchase #5	$145.44	4.333%	$151.7419	$151.74	$151.75	$151.70
Purchase #6	$197.96	9.646%	$217.0552	$217.06	$217.05	$217.10
Purchase #7	$27.57	13.460%	$31.2809	$31.28	$31.30	$31.30
7 purchase totals =	$749.18		$808.0815	$808.08	$808.10	$808.10