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	$121.53	12.444%	$136.6532	$136.65	$136.65	$136.70
Purchase #2	$100.69	4.429%	$105.1496	$105.15	$105.15	$105.10
Purchase #3	$34.60	8.679%	$37.6029	$37.60	$37.60	$37.60
Purchase #4	$103.97	12.304%	$116.7625	$116.76	$116.75	$116.80
Purchase #5	$231.33	4.459%	$241.645	$241.65	$241.65	$241.60
Purchase #6	$244.27	4.179%	$254.478	$254.48	$254.50	$254.50
Purchase #7	$241.98	7.350%	$259.7655	$259.77	$259.75	$259.80
7 purchase totals =	$1,078.37		$1,152.0567	$1,152.06	$1,152.05	$1,152.10