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	$95.95	8.248%	$103.864	$103.86	$103.85	$103.90
Purchase #2	$76.93	8.114%	$83.1721	$83.17	$83.15	$83.20
Purchase #3	$189.35	10.670%	$209.5536	$209.55	$209.55	$209.60
Purchase #4	$45.27	3.496%	$46.8526	$46.85	$46.85	$46.90
Purchase #5	$188.72	7.362%	$202.6136	$202.61	$202.60	$202.60
Purchase #6	$105.82	12.802%	$119.3671	$119.37	$119.35	$119.40
Purchase #7	$104.33	6.856%	$111.4829	$111.48	$111.50	$111.50
7 purchase totals =	$806.37		$876.9059	$876.89	$876.85	$877.10