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	$102.74	10.290%	$113.3119	$113.31	$113.30	$113.30
Purchase #2	$169.55	7.756%	$182.7003	$182.70	$182.70	$182.70
Purchase #3	$162.87	12.461%	$183.1652	$183.17	$183.15	$183.20
Purchase #4	$67.32	5.470%	$71.0024	$71.00	$71.00	$71.00
Purchase #5	$142.30	10.646%	$157.4493	$157.45	$157.45	$157.40
Purchase #6	$141.80	7.572%	$152.5371	$152.54	$152.55	$152.50
Purchase #7	$95.96	3.558%	$99.3743	$99.37	$99.35	$99.40
7 purchase totals =	$882.54		$959.5405	$959.54	$959.50	$959.50